Hydrogen purification membranes, components and fuel processing systems containing the same

ABSTRACT

Hydrogen-producing fuel processing systems, hydrogen purification membranes, hydrogen purification devices, and fuel processing and fuel cell systems that include hydrogen purification devices. In some embodiments, the fuel processing systems and the hydrogen purification membranes include a metal membrane, which is at least substantially comprised of palladium or a palladium alloy. In some embodiments, the membrane contains trace amounts of carbon, silicon, and/or oxygen. In some embodiments, the membranes form part of a hydrogen purification device that includes an enclosure containing a separation assembly, which is adapted to receive a mixed gas stream containing hydrogen gas and to produce a stream that contains pure or at least substantially pure hydrogen gas therefrom. In some embodiments, the membrane(s) and/or purification device forms a portion of a fuel processor, and in some embodiments, the membrane(s) and/or purification device forms a portion of a fuel processing or fuel cell system.

RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 11/441,931, which was filed on May 25, 2006, issuedon Mar. 27, 2007 as U.S. Pat. No. 7,195,663, and which is a continuationof U.S. patent application Ser. No. 10/989,907, which was filed on Nov.15, 2004, issued on May 30, 2006 as U.S. Pat. No. 7,052,530, and whichis a continuation of U.S. patent application Ser. No. 10/728,473, nowU.S. Pat. No. 6,824,593, which was filed on Dec. 5, 2003, and which is acontinuation of U.S. patent application Ser. No. 10/430,110, now U.S.Pat. No. 6,723,156, which was filed on May 5, 2003, and which is acontinuation of U.S. patent application Ser. No. 10/371,597, now U.S.Pat. No. 6,632,270, which was filed on Feb. 20, 2003, and which is acontinuation of U.S. patent application Ser. No. 10/027,509, now U.S.Pat. No. 6,537,352, which was filed on Dec. 19, 2001. U.S. patentapplication Ser. No. 10/027,509 is a continuation-in-part of and claimspriority to U.S. patent application Ser. Nos. 09/839,997, 09/618,866,and 09/967,172. U.S. patent application Ser. No. 09/839,997, was filedon Apr. 20, 2001 now U.S. Pat. No. 6,783,741 and is a continuation ofU.S. patent application Ser. No. 09/291,447, now U.S. Pat. No.6,221,117, which was filed on Apr. 13, 1999 and which is acontinuation-in-part application of U.S. patent application Ser. No.08/951,091, now U.S. Pat. No. 5,997,594, which was filed on Oct. 15,1997, and which is a continuation-in-part application of U.S. patentapplication Ser. No. 08/741,057, now U.S. Pat. No. 5,861,137, which wasfiled on Oct. 30, 1996. U.S. patent application Ser. No. 09/618,866, nowU.S. Pat. No. 6,547,858, was filed on Jul. 19, 2000 and is acontinuation-in-part application of U.S. patent application Ser. No.09/274,154, now U.S. Pat. No. 6,152,995, which was filed on Mar. 22,1999. U.S. patent application Ser. No. 09/967,172, now U.S. Pat. No.6,494,937, was filed on Sep. 27, 2001. The complete disclosures of theabove-identified patent applications are hereby incorporated byreference for all purposes.

FIELD OF THE DISCLOSURE

The present invention is related generally to the purification ofhydrogen gas, and more specifically to hydrogen purification membranes,devices, and fuel processing and fuel cell systems containing the same.

BACKGROUND OF THE DISCLOSURE

Purified hydrogen is used in the manufacture of many products includingmetals, edible fats and oils, and semiconductors and microelectronics.Purified hydrogen is also an important fuel source for many energyconversion devices. For example, fuel cells use purified hydrogen and anoxidant to produce an electrical potential. Various processes anddevices may be used to produce the hydrogen gas that is consumed by thefuel cells. However, many hydrogen-production processes produce animpure hydrogen stream, which may also be referred to as a mixed gasstream that contains hydrogen gas. Prior to delivering this stream to afuel cell, a stack of fuel cells, or another hydrogen-consuming device,the mixed gas stream may be purified, such as to remove undesirableimpurities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a hydrogen purification device.

FIG. 2 is an isometric view of a hydrogen-permeable metal membrane.

FIG. 3 is a cross-sectional detail of the membrane of FIG. 2 with anattached frame.

FIG. 4 is an isometric view of the membrane of FIG. 2 after being etchedaccording to a method of the present invention.

FIG. 5 is a cross-sectional detail of the membrane of FIG. 4.

FIG. 6 is an isometric view of the membrane of FIG. 2 with an absorbentmedium placed over an application region of one of the membrane'ssurfaces.

FIG. 7 is a cross-sectional detail of the membrane of FIG. 6.

FIG. 8 is the detail of FIG. 4 with a hole indicated generally at 41 andthe repaired hole indicated in dashed lines at 43.

FIG. 9 is a schematic cross-sectional view of a hydrogen purificationdevice having a planar separation membrane.

FIG. 10 is an isometric view of an illustrative end plate for a hydrogenpurification device according to the present invention.

FIG. 11 is a schematic cross-sectional view of a hydrogen purificationdevice having a tubular separation membrane.

FIG. 12 is a schematic cross-sectional view of another hydrogenpurification device having a tubular separation membrane.

FIG. 13 is a schematic cross-sectional view of another enclosure for ahydrogen purification device constructed according to the presentinvention.

FIG. 14 is a schematic cross-sectional view of another enclosure for ahydrogen purification device constructed according to the presentinvention.

FIG. 15 is a fragmentary cross-sectional detail showing another suitableinterface between components of an enclosure for a purification deviceaccording to the present invention.

FIG. 16 is a fragmentary cross-sectional detail showing another suitableinterface between components of an enclosure for a purification deviceaccording to the present invention.

FIG. 17 is a fragmentary cross-sectional detail showing another suitableinterface between components of an enclosure for a purification deviceaccording to the present invention.

FIG. 18 is a fragmentary cross-sectional detail showing another suitableinterface between components of an enclosure for a purification deviceaccording to the present invention.

FIG. 19 is a top plan view of an end plate for a hydrogen purificationdevice constructed according to the present invention.

FIG. 20 is a cross-sectional view of the end plate of FIG. 19.

FIG. 21 is a top plan view of an end plate for a hydrogen purificationdevice constructed according to the present invention.

FIG. 22 is a cross-sectional view of the end plate of FIG. 21.

FIG. 23 is a top plan view of an end plate for a hydrogen purificationdevice constructed according to the present invention.

FIG. 24 is a cross-sectional view of the end plate of FIG. 23.

FIG. 25 is a top plan view of an end plate for an enclosure for ahydrogen purification device constructed according to the presentinvention.

FIG. 26 is a side elevation view of the end plate of FIG. 25.

FIG. 27 is a partial cross-sectional side elevation view of an enclosurefor a hydrogen purification device constructed with a pair of the endplates shown in FIGS. 25-26.

FIG. 28 is an isometric view of another hydrogen purification deviceconstructed according to the present invention.

FIG. 29 is a cross-sectional view of the device of FIG. 28.

FIG. 30 is a side elevation view of another end plate for a hydrogenpurification device constructed according to the present invention.

FIG. 31 is a side elevation view of another end plate for a hydrogenpurification device constructed according to the present invention.

FIG. 32 is a side elevation view of another end plate for a hydrogenpurification device constructed according to the present invention.

FIG. 33 is a fragmentary side elevation view of a pair of separationmembranes separated by a support.

FIG. 34 is an exploded isometric view of a membrane envelope constructedaccording to the present invention and including a support in the formof a screen structure having several layers.

FIG. 35 is an exploded isometric view of another membrane envelopeaccording to the present invention.

FIG. 36 is an exploded isometric view of another membrane envelopeconstructed according to the present invention.

FIG. 37 is an exploded isometric view of another membrane envelopeconstructed according to the present invention.

FIG. 38 is a cross-sectional view of a shell for an enclosure for ahydrogen purification device constructed according to the presentinvention with an illustrative membrane frame and membrane module shownin dashed lines.

FIG. 39 is a top plan view of the end plate of FIG. 21 with anillustrative separation membrane and frame shown in dashed lines.

FIG. 40 is a top plan view of the end plate of FIG. 25 with anillustrative separation membrane and frame shown in dashed lines.

FIG. 41 is an exploded isometric view of another hydrogen purificationdevice constructed according to the present invention.

FIG. 42 is a schematic diagram of a fuel processing system that includesa fuel processor and a hydrogen purification device constructedaccording to the present invention.

FIG. 43 is a schematic diagram of a fuel processing system that includesa fuel processor integrated with a hydrogen purification deviceaccording to the present invention.

FIG. 44 is a schematic diagram of another fuel processor that includesan integrated hydrogen purification device constructed according to thepresent invention.

FIG. 45 is a schematic diagram of a fuel cell system that includes ahydrogen purification device constructed according to the presentinvention.

FIG. 46 is a cross-sectional view showing an example of a steam reformerconstructed according to the present invention.

FIG. 47 is a cross-sectional view showing another example of a steamreformer constructed according to the present invention.

FIG. 48 is a cross-sectional view showing another example of a steamreformer constructed according to the present invention.

FIG. 49 is a cross-sectional view showing another example of a steamreformer constructed according to the present invention.

FIG. 50 is a cross-sectional view showing another example of a steamreformer constructed according to the present invention.

FIG. 51 is a cross-sectional view showing another example of a steamreformer constructed according to the present invention.

DETAILED DESCRIPTION AND BEST MODE OF THE DISCLOSURE

A hydrogen purification device is schematically illustrated in FIG. 1and generally indicated at 10. Device 10 includes a body, or enclosure,12 that defines an internal compartment 18 in which a separationassembly 20 is positioned. A mixed gas stream 24 containing hydrogen gas26 and other gases 28 is delivered to the internal compartment. Morespecifically, the mixed gas stream is delivered to a mixed gas region 30of the internal compartment and into contact with separation assembly20. Separation assembly 20 includes any suitable structure adapted toreceive the mixed gas stream and to produce therefrom a permeate, orhydrogen-rich, stream. Stream 34 typically will contain pure or at leastsubstantially pure hydrogen gas. However, it within the scope of thedisclosure that stream 34 may at least initially also include a carrier,or sweep, gas component.

In the illustrated embodiment, the portion of the mixed gas stream thatpasses through the separation assembly enters a permeate region 32 ofthe internal compartment. This portion of the mixed gas stream formshydrogen-rich stream 34, and the portion of the mixed gas stream thatdoes not pass through the separation assembly forms a byproduct stream36, which contains at least a substantial portion of the other gases. Insome embodiments, byproduct stream 36 may contain a portion of thehydrogen gas present in the mixed gas stream. It is also within thescope of the disclosure that the separation assembly is adapted to trapor otherwise retain at least a substantial portion of the other gases,which will be removed as a byproduct stream as the assembly is replaced,regenerated or otherwise recharged. In FIG. 1, streams 24-28 are meantto schematically represent that each of streams 24-28 may include morethat one actual stream flowing into or out of device 10. For example,device 10 may receive plural feed streams 24, a single stream 24 that isdivided into plural streams prior to contacting separation assembly 20,or simply a single stream that is delivered into compartment 18.

Device 10 is typically operated at elevated temperatures and/orpressures. For example, device 10 may be operated at (selected)temperatures in the range of ambient temperatures up to 700° C. or more.In many embodiments, the selected temperature will be in the range of200° C. and 500° C., in other embodiments, the selected temperature willbe in the range of 250° C. and 400° C. and in still other embodiments,the selected temperature will be 400° C.±either 25° C., 50° C. or 75° C.Device 10 may be operated at (selected) pressures in the range ofapproximately 50 psi and 1000 psi or more. In many embodiments, theselected pressure will be in the range of 50 psi and 250 or 500 psi, inother embodiments, the selected pressure will be less than 300 psi orless than 250 psi, and in still other embodiments, the selected pressurewill be 175 psi±either 25 psi, 50 psi or 75 psi. As a result, theenclosure must be sufficiently well sealed to achieve and withstand theoperating pressure.

It should be understood that as used herein with reference to operatingparameters like temperature or pressure, the term “selected” refers todefined or predetermined threshold values or ranges of values, withdevice 10 and any associated components being configured to operate ator within these selected values. For further illustration, a selectedoperating temperature may be an operating temperature above or below aspecific temperature, within a specific range of temperatures, or withina defined tolerance from a specific temperature, such as within 5%, 10%,etc. of a specific temperature.

In embodiments of the hydrogen purification device in which the deviceis operated at an elevated operating temperature, heat needs to beapplied to, or generated within, the device to raise the temperature ofthe device to the selected operating temperature. For example, this heatmay be provided by any suitable heating assembly 42. Illustrativeexamples of heating assembly 42 have been schematically illustrated inFIG. 1. It should be understood that assembly 42 may take any suitableform, including mixed gas stream 24 itself. Illustrative examples ofother suitable heating assemblies include one or more of a resistanceheater, a burner or other combustion region that produces a heatedexhaust stream, heat exchange with a heated fluid stream other thanmixed gas stream 24, etc. When a burner or other combustion chamber isused, a fuel stream is consumed and byproduct stream 36 may form all ora portion of this fuel stream. At 42′ in FIG. 1, schematicrepresentations have been made to illustrate that the heating assemblymay deliver the heated fluid stream external device 10, such as within ajacket that surrounds or at least partially surrounds the enclosure, bya stream that extends into the enclosure or through passages in theenclosure, or by conduction, such as with an electric resistance heateror other device that radiates or conducts electrically generated heat.

A suitable structure for separation assembly 20 is one or morehydrogen-permeable and/or hydrogen-selective membranes 46, such assomewhat schematically illustrated in FIG. 2. As shown, membrane 46includes a pair of generally opposed surfaces 2 and an edge 4 joiningthe perimeters of the surfaces. Each surface 2 includes an outer edgeregion 6 that surrounds a central region 8. Membrane 46 is typicallyroll formed and, as shown, has a generally rectangular, sheet-likeconfiguration with a constant thickness. It should be understood thatmembrane 46 may have any geometric or irregular shape, such as bycutting the formed membrane into a desired shape based on userpreferences or application requirements. It is within the scope of thedisclosure that any suitable method for forming membrane 46 may be used.For example, membrane 46 may also be formed from such processes aselectro deposition, sputtering or vapor deposition.

In FIG. 3, membrane 46 is shown in cross-section, and it can be seenthat the thickness 11 of the membrane measured between the centralregions is the same as the thickness 13 measured between the edgeregions. In the figures, it should be understood that the thicknesses ofthe membranes and subsequently described absorbent media and frame havebeen exaggerated for purposes of illustration. Typically,hydrogen-permeable membranes have thicknesses less than approximately 50microns, although the disclosed etching process may be used with thickermembranes.

Membrane 46 may be formed of any hydrogen-permeable material suitablefor use in the operating environment and parameters in whichpurification device 10 is operated. Examples of suitable materials formembranes 46 include palladium and palladium alloys, and especially thinfilms of such metals and metal alloys. Palladium alloys have provenparticularly effective, especially palladium with 35 wt % to 45 wt %copper. More specific examples of a palladium alloy that have proveneffective include palladium-copper alloys containing 40 wt % (+/−0.25 or0.5 wt %) copper, although other alloys and percentages are within thescope of the disclosure. Membranes 46 are typically formed from a thinfoil that is approximately 0.001 inches thick. Accordingly, it should beunderstood that the thicknesses of the membranes illustrated herein havebeen exaggerated for purposes of illustration. It is within the scope ofthe present disclosure, however, that the membranes may be formed fromhydrogen-permeable and/or hydrogen-selective materials, including metalsand metal alloys other than those discussed above as well asnon-metallic materials and compositions.

Metal membranes according to the present disclosure, and especiallypalladium and palladium alloy membranes, typically will also includerelatively small amounts of at least one of carbon, silicon and oxygen,typically ranging from a few parts per million (ppm) to several hundredor more parts per million. For example, carbon may be introduced to themembrane either intentionally or unintentionally, such as from the rawmaterials from which the membranes are formed and/or through thehandling and formation process. Because many lubricants arecarbon-based, the machinery used in the formation and processing of themembranes may introduce carbon to the material from which the membranesare formed. Similarly, carbon-containing oils may be transferred to thematerial by direct or indirect contact with a user's body. Preferably,membranes constructed according to the present disclosure include lessthan 250 ppm carbon, and more preferably less than 150, 100 or 50 ppmcarbon. Nonetheless, the membranes will typically still contain somecarbon content, such as at least 5 or 10 ppm carbon. Therefore, it iswithin the scope of the disclosure that the membranes will containcarbon concentrations within the above ranges, such as approximately5-150 or 10-150 ppm, 5-100 or 10-100 ppm, or 5-50 or 10-50 ppm carbon.

It is further within the scope of the disclosure that the membranes mayinclude trace amounts of silicon and/or oxygen. For example, oxygen maybe present in the Pd40Cu (or other alloy or metal) material inconcentrations within the range of 5-200 ppm, including ranges of 5-100,10-100, 5-50 and 10-50 ppm. Additionally or alternatively, silicon maybe present in the material in concentrations in the range of 5-100 ppm,including ranges of 5-10 and 10-50 ppm.

In experiments, reducing the concentration of carbon in the membranesresults in an increase in hydrogen flux, compared to a similar membranethat is used in similar operating conditions but which contains agreater concentration of carbon. Similarly, it is expected thatincreasing the oxygen and/or silicon concentrations will detrimentallyaffect the mechanical properties of the membrane. The following tabledemonstrates the correlation between high hydrogen permeability(represented as hydrogen flux through a 25 micron thick membrane at 100psig hydrogen, 400 degrees Celsius) and low carbon content.

TABLE 1 Hydrogen flux through 25 micron thick Pd—40Cu membranescontaining trace amounts of carbon, oxygen and silicon at 400° C. and100 psig hydrogen Hydrogen Flux Concentration (ppm) (std ft³/ft² · hr)Carbon Oxygen Silicon 130 40 25 10 125 56 29 39 115 146 25 15 56 219 2527

It is within the scope of the disclosure that the membranes may have avariety of thicknesses, including thicknesses that are greater or lessthan discussed above. For example, the membrane may be made thinner,with commensurate increase in hydrogen flux. Examples of suitablemechanisms for reducing the thickness of the membranes include rolling,sputtering and etching. A suitable etching process is disclosed in U.S.Pat. No. 6,152,995, the complete disclosure of which is herebyincorporated by reference for all purposes. Examples of variousmembranes, membrane configurations, and methods for preparing the sameare disclosed in U.S. Pat. Nos. 6,221,117 and 6,319,306, the completedisclosures of which are hereby incorporated by reference for allpurposes. The above-described “trace” components (carbon, oxygen and/orsilicon) may be described as being secondary components of the materialfrom which the membranes are formed, with palladium or a palladium alloybeing referred to as the primary component. In practice, it is withinthe scope of the disclosure that these trace components may be alloyedwith the palladium or palladium alloy material from which the membranesare formed or otherwise distributed or present within the membranes.

As discussed, membrane 46 may be formed of a hydrogen-permeable metal ormetal alloy, such as palladium or a palladium alloy, including apalladium alloy that is essentially comprised of 60 wt % palladium and40 wt % copper. Because palladium and palladium alloys are expensive,the thickness of the membrane should be minimal; i.e., as thin aspossible without introducing an excessive number of holes in themembrane if it is desirable to reduce the expense of the membranes.Holes in the membrane are not desired because holes allow all gaseouscomponents, including impurities, to pass through the membrane, therebycounteracting the hydrogen-selectivity of the membrane.

An example of a method for reducing the thickness of ahydrogen-permeable membrane is to roll form the membrane to be verythin, such as with thicknesses of less than approximately 50 microns,and more commonly with thicknesses of approximately 25 microns. The fluxthrough a hydrogen-permeable metal membrane is inversely proportional tothe membrane thickness. Therefore, by decreasing the thickness of themembrane, it is expected that the flux through the membrane willincrease, and vice versa. In Table 2, below, the expected flux ofhydrogen through various thicknesses of Pd-40Cu membranes is shown.

TABLE 2 Expected hydrogen flux through Pd—40Cu membranes at 400° C. and100 psig hydrogen feed, permeate hydrogen at ambient pressure. MembraneThickness Expected Hydrogen Flux 25 micron 60 mL/cm² · min 17 micron 88mL/cm² · min 15 micron 100 mL/cm² · min 

Besides the increase in flux obtained by decreasing the thickness of themembrane, the cost to obtain the membrane also increases as themembrane's thickness is reduced. Also, as the thickness of a membranedecreases, the membrane becomes more fragile and difficult to handlewithout damaging.

Through the etching process, or method, of the present disclosure,discussed in more detail subsequently, the thickness of a portion of themembrane, such as central region 8, may be selectively reduced, whileleaving the remaining portion of the membrane, such as edge region 6, atits original thickness. Therefore, greater flux is obtained in thethinner etched region, while leaving a thicker, more durable edge regionthat bounds the central region and thereby provides support to themembrane.

For example, an etched membrane 46 prepared according to an etchingmethod of the present disclosure is shown in FIG. 4 and illustratedgenerally at 17. Similar to the other membranes 46 described andillustrated herein, membrane 17 includes a pair of generally opposedsurfaces 19 and an edge 23 joining the surfaces. Each surface 19includes an outer edge region 25 that surrounds a central region 27.Membrane 17 is formed from any of the above-discussed hydrogen-permeablemetal materials, and may have any of the above-discussed configurationsand shapes. The etching process works effectively on work-hardened, ornon-annealed membranes. Alternatively, the membrane may be annealedprior to the etching process. Unlike an unetched embodiment of membrane46, however, the thickness of membrane 17 measured between centralregions 27 is less than the thickness 31 measured between the edgeregions, as schematically illustrated in FIG. 5. Therefore, the hydrogenflux through the central region will be greater than that through theedge region, as expected from the above discussion of the inverselyproportional relationship between membrane thickness and hydrogen flux.

However, an unexpected benefit of chemically etching the membrane, asdisclosed herein, is that the hydrogen flux through the etched regionexceeds that expected or measured through roll-formed membranes of equalthickness. As shown below in Table 3, the method of the presentdisclosure yields a hydrogen-permeable metal membrane with significantlygreater flux than unetched membranes of similar thicknesses.

TABLE 3 Hydrogen flux through etched and unetched Pd—40Cu membranes at400° C. and 100 psig hydrogen feed, permeate hydrogen at ambientpressure. Aqua regia etchant. Etching Membrane Observed Expected TimeThickness Hydrogen Flux Hydrogen Flux None 25 micron 60 mL/cm² · min 60mL/cm² · min 2.0 mins 17 micron 94 mL/cm² · min 88 mL/cm² · min 2.5 mins15 micron 122 mL/cm² · min  100 mL/cm² · min 

As the above table demonstrates, the invented method produceshydrogen-permeable metal membranes that permit increased hydrogenthroughput compared to unetched membranes of similar thickness byincreasing the roughness and surface area of the etched region of themembrane. Perhaps more importantly, this increase in throughput isachieved without sacrificing selectivity for hydrogen or the purity ofthe harvested hydrogen gas, which is passed through the membrane.

Increasing the surface roughness of the membrane is especiallybeneficial as the thickness of the membrane is reduced to less than 25microns, especially less than 20 microns. As the membrane thickness isreduced, the surface reaction rates governing the transport of gaseousmolecular hydrogen onto the surface of the metal membrane become moreimportant to the overall permeation rate of hydrogen across themembrane. In extreme cases in which the membrane is quite thin (lessthan approximately 15 microns) the surface reaction rates aresignificant in governing the overall permeation rate of hydrogen acrossthe membrane. Therefore, increasing the surface area increases the rateof hydrogen permeation. This contrasts with relatively thick membranes(greater than 25 microns) in which the surface reaction rates are lessimportant and the overall permeation rate of hydrogen across themembrane is governed by the bulk diffusion of hydrogen through themembrane.

Thus the etching process results in an overall reduction in thethickness of the membrane and an increase in the surface roughness (andsurface area) of the membrane. These improvements yield an increase inhydrogen flux and reduce the amount of material (e.g., palladium alloy)that is required, while still maintaining the membrane's selectivity forhydrogen.

In the invented etching process, an etchant is used to selectivelyreduce the thickness of the membrane. When the etchant removes, oretches, material from the surface of a membrane, the etchant alsoincreases the surface roughness and surface area of the membrane in theetched region.

Examples of suitable etchants include oxidizing agents and acids. Anexample of a suitable oxidizing acid is nitric acid. Other suitableexamples include combinations of nitric acid with other acids, such asaqua regia (a mixture of 25 vol % concentrated nitric acid and 75 vol %concentrated hydrochloric acid). Another specific example of an etchantwell-suited to use in the present disclosure is a mixture comprising 67wt % concentrated nitric acid and 33 wt % aqueous solution of poly(vinylalcohol). A suitable method of preparing the aqueous solution ofpoly(vinyl alcohol) is to dissolve 4 wt % of poly(vinyl alcohol)(average molecular weight 124,000 to 186,000; 87% to 89% hydrolyzed;Aldrich Chemical Company, Milwaukee, Wis.) in de-ionized water. Thedisclosed examples of etchants are for illustrative purposes, and shouldnot be construed to be limiting examples. For example, the relativepercentage of acid may be increased or decreased to make the etchantrespectively more or less reactive, as desired.

In a first method of the present disclosure, a selected etchant isapplied to at least one of the surfaces of the membrane. Once applied,the etchant removes material from the surface of the membrane, therebyincreasing its surface roughness and reducing the thickness of themembrane in the etched region. After a defined time period, the etchantis removed. The etching process disclosed herein typically is conductedunder ambient conditions (temperature and pressure), although it shouldbe understood that the process could be conducted at elevated or reducedtemperatures and pressures as well.

The etching process is limited either by the time during which themembrane is exposed to the etchant, or by the reactive elements of theetchant. In the latter scenario, it should be understood that theetching reaction is self-limiting, in that the reaction will reach anequilibrium state in which the concentration of dissolved membrane inthe etchant solution remains relatively constant. Regardless of thelimiting factor in the process, it is important to apply a volume andconcentration of etchant for a time period that will not result in theetchant creating substantial holes in, or completely dissolving, themembrane. Preferably, no holes are created in the membrane during theetching process.

When applying the etchant to a surface of membrane 46, such as toproduce membrane 17, it is desirable to control the region of thesurface over which the etchant extends. It is also desirable to maintainan even distribution of etchant over this application region. If theapplication region of the etchant is not controlled, then the etchantmay remove material from other non-desired regions of the membrane, suchas the edge region, or may damage materials joined to the membrane, suchas an attached frame. If an even distribution of etchant is notmaintained, areas of increased etchant may have too much materialremoved, resulting in holes in the membrane. Similarly, other areas maynot have enough material removed, resulting in less than the desiredreduction in thickness and increase in flux.

To control the distribution of etchant within the desired applicationregion, an absorbent medium is placed on the membrane and defines anapplication region to be etched. For example, in FIGS. 6 and 7, theabsorbent medium is generally indicated at 33 and covers applicationregion 35 of surface 2. As shown, medium 33 is sized to cover only acentral portion of surface 2, however, it should be understood thatmedium 33 may be selectively sized to define application regions of anydesired size and shape, up to the complete expanse of surface 2.Typically, however, only a central portion of each surface is treated,leaving an unetched perimeter of greater thickness than the centralregion. This unetched region, because of its greater thickness, providesstrength and support to membrane 46 while still contributing to thehydrogen permeability of the membrane.

Besides being selected to absorb the particular etchant withoutadversely reacting to the etchant or metal membrane, it is preferablethat medium 33 has a substantially uniform absorbency and diffusivityalong its length. When medium 33 absorbs and distributes the etchantuniformly along its length, it distributes the etchant evenly across theapplication region, thereby removing substantially the same amount ofmaterial across the entire application region. The benefit of this isnot only that some etchant will contact, and thereby remove materialfrom the entire application region, but also that the etchant will beuniformly distributed across the application region. Therefore, medium33 prevents too much etchant being localized in an area, which wouldresult in too much material being removed. In a region where too muchetchant is applied, the excess etchant is drawn away from that region toother areas of the medium where less etchant is applied. Similarly, in aregion where too little etchant is applied, the medium draws etchant tothat region to produce an even distribution across the medium, andthereby across the application region.

As a result, the reduction of thickness in membrane 46 will berelatively uniform across the application region, and perhaps, moreimportantly, will be reproducible regardless of the exact rate andposition at which the etchant is applied. Therefore, with the same sizeand type of medium 33 and the same volume of etchant 37, the resultingreduction in thickness should be reproducible for membranes of the samecomposition. Of course, it should be understood that etching removesmaterial from the surface of the membrane, thereby resulting in anuneven, rough surface with increased surface area over an unetchedsurface. Therefore, the exact surface topography will not be seen.However, the average thickness measured across a section of the membraneshould be reproducible. For example, in FIG. 5, the average thicknessbetween central regions 27 is indicated with dashed lines.

Because medium 33 essentially defines the bounds of application region35, medium 33 should be sized prior to placing it upon the surface to beetched. After placing the medium in the desired position on one of themembrane's surfaces, such as surface 2 shown in FIG. 6, a volume ofetchant is applied. In FIG. 6, the applied volume of etchant isschematically illustrated at 37, with arrows 39 illustrating theabsorption and distribution of etchant 37 across medium 33.

The applied volume of etchant should be no more than a saturation volumeof etchant. An absorbent medium can only absorb up to a defined volumeof a particular etchant per unit of medium 33 before reaching thesaturation point of the medium. Therefore, it is important not to exceedthis saturation point. Too much applied etchant will result inunabsorbed etchant pooling on or adjacent to the medium, such as on theupper surface of medium 33 or around the edges of the medium. Whenexcess etchant contacts the surface, it is likely to result in holes inthe membrane because more than the desired amount of material isremoved. As discussed, if these holes are numerous or large enough, theywill render the membrane unusable for hydrogen purificationapplications, with any holes lowering the purity of the hydrogen passingthrough the membrane.

Therefore, to prevent too much etchant from being applied, the volume ofetchant applied may approach, but should not exceed, the saturationvolume of the etchant.

An example of a suitable absorbent medium is a cellulosic material, suchas absorbent paper products. A particular example of an absorbent mediumthat has proven effective are single-fold paper towels manufactured bythe Kimberly Clark company. When a three inch by three inch area of sucha towel is used, approximately 2.5 mL of etchant may be applied withoutexceeding the saturation volume of that area. The capillary action ofthe cellulosic towel both absorbs the applied etchant and distributesthe etchant throughout the towel. Other paper and cellulosic materialsmay be used as well, as long as they meet the criteria defined herein.Absorbent, diffusive materials other than cellulosic materials may beused as well.

After applying the etchant to medium 33, the etchant is allowed toremove material from the application region for a determined timeperiod. This period is best determined through experimentation and willvary depending on such factors as the composition, thickness and desiredthickness of the membrane, the absorbent medium being used, thecomposition and concentration of etchant, and the temperature at whichthe etching process is conducted. After this time period has passed, themedium is removed from the membrane, and the application, or treatmentarea is rinsed with water to remove any remaining etchant. Afterrinsing, the method may be repeated to etch another surface of themembrane.

Instead of a single etching step on each surface of the membrane, avariation of the above method includes plural etching steps for eachsurface to be etched. In the first step, a more reactive, or vigorousetchant is used to remove a substantial portion of the material to beremoved. In the second step, a less reactive etchant is used to providea more controlled, even etch across the application region.

As an illustrative example, Pd-40Cu alloy foil was etched first withconcentrated nitric acid for 20-30 seconds using the absorbent mediumtechnique described above. After removing the medium and rinsing anddrying the membrane, a second etch with a mixture of 20 vol % neatethylene glycol and the balance concentrated nitric acid was performedfor between 1 and 4 minutes. Subsequent etching steps were performedwith the glycol mixture to continue to gradually reduce the thickness ofthe membrane in the application region. Results of etching Pd-40Cu foilusing this method are given in the table below.

TABLE 4 Results of etching Pd—40Cu membrane with concentrated nitricacid for 30 seconds followed by subsequent etches with concentratednitric acid diluted with 20% vol ethylene glycol. Etching SolutionEtching Time Observations None (Virgin Pd—40Cu Foil) N/A Measures 0.0013inches thick 1) Conc. Nitric Acid 1) 30 seconds Measures 0.0008 to 2) 20vol % ethylene 2) 1.5 minutes 0.0009 inches thick, glycol/HNO₃ no pinholes 1) Conc. Nitric Acid 1) 30 seconds Measures 0.0005 to 2) 20 vol %ethylene 2) 1.5 minutes 0.0006 inches thick, glycol/HNO₃ no pin holes 3)20 vol % ethylene 3) 1.5 minutes glycol/HNO₃ 1) Conc. Nitric Acid 1) 30seconds Measures 0.0005 2) 20 vol % ethylene 2) 3 minutes inches thick,no pin glycol/HNO₃ holes in membrane 1) Conc. Nitric Acid 1) 1 minuteMultiple pin holes in 2) 20 vol % ethylene 2) 3 minutes membraneglycol/HNO₃

Other than confining the etching solution to a desired applicationregion, another benefit of using an absorbent medium to control theplacement and distribution of the etchant is that the quantity ofetchant (or etching solution) that may be applied without oversaturatingthe medium is limited. Thus, the etching reaction may be self-limiting,depending on the choice of and composition of etchant. For instance,varying the etching time using 33.3 wt % PVA solution/66.7 wt %concentrated HNO₃ yielded the results shown in the following table.These results indicate that the volume of etchant that is applied at onetime may limit the depth of etching, so long as the etchant is not soreactive or applied in sufficient quantity to completely dissolve theapplication region.

TABLE 5 Results of etching Pd—40Cu membrane with a solution of 33.3 wt %PVA solution/66.7 wt % concentrated nitric acid. Etching TimeObservations 0 Measures 0.0013 inches thick 3 minutes Measures 0.0011inches thick 4 minutes Measures 0.0011 inches thick 5 minutes Measures0.0011 inches thick 6 minutes Measures 0.0011 inches thick 3 minutes,rinse, 3 minutes Measures 0.0008 to 0.0009 inches thick 3 minutes,rinse, 3 minutes, Measures 0.0006 inches thick, rinse, 3 minutesmultiple pin holes

In a further variation of the etching method, a suitable mask may beapplied to the membrane to define the boundaries of the region to beetched. For example, in FIG. 6, instead of using absorbent medium 33 todefine application region 35, a non-absorbent mask could be appliedaround edge region 25. Because this mask does not absorb the etchant, itconfines the etchant to an application region bounded by the mask.Following etching, the mask is removed. The mask may be applied as aliquid or it may be a film with an adhesive to bond the film to themembrane.

If the chemical etching process is not properly controlled, tiny holeswill appear in the membrane. For example, in FIG. 8 membrane 17 is shownwith a hole 41 in its central region 27. Typically, the holes will bevery small, however, the size of a particular hole will depend on theconcentration and quantity of etchant applied to that region, as well asthe time during which the etchant was allowed to etch material from themembrane. Holes, such as hole 41, reduce the purity of the hydrogen gasharvested through the membrane, as well as the selectivity of themembrane for hydrogen. The probability of holes forming in the membraneduring the etching process increases as the thickness of the membrane isreduced. Therefore, there is often a need to repair any holes formedduring the etching process.

One method for detecting any such holes is to utilize a light source toidentify holes in the membrane. By shining a light on one side of themembrane, holes are detected where light shines through the other sideof the membrane. The detected holes may then be repaired by spotelectroplating, such as by using a Hunter Micro-Metallizer Pen availablefrom Hunter Products, Inc., Bridgewater, N.J. In FIG. 7, a patch, orplug, 43 is generally indicated in dashed lines and shown repairing hole41. Any other suitable method may be used for repairing tiny holesresulting from etching the membrane.

The repairing step of the invented etching process also may be performedusing a photolithographic method. In this case a light-sensitive,electrically insulating mask is applied to one surface of the membrane,and then the membrane is irradiated with light of the appropriatewavelength(s) from the opposite side. Any tiny holes that might bepresent in the membrane will allow the light to pass through themembrane and be absorbed by the light-sensitive mask. Next, the mask iswashed to remove irradiated regions of the mask and thereby reveal thebare metal of the membrane. Because only the irradiated regions of themask are removed, the remaining mask serves as an electrical insulatorover the surface of the membrane. Then, all of the spots where the maskhas been removed are electroplated or electrolessplated at the sametime.

Because the patch, or plug, represents only a minute percentage of thesurface area of the membrane, the patch may be formed from a materialthat is not hydrogen-permeable without the flux through the membranebeing noticeably affected. Of course, a hydrogen-permeable and selectivepatch is preferred. Suitable metals for electroplating to fill or closetiny holes in the palladium-alloy membranes include copper, silver,gold, nickel, palladium, chromium, rhodium, and platinum. Volatilemetals such as zinc, mercury, lead, bismuth and cadmium should beavoided. Furthermore, it is preferable that metal applied by plating berelatively free of phosphorous, carbon, sulfur and nitrogen, since theseheteroatoms could contaminate large areas of the membrane and aregenerally known to reduce the permeability of palladium alloys tohydrogen.

In use, membrane 46 provides a mechanism for removing hydrogen frommixtures of gases because it selectively allows hydrogen to permeatethrough the membrane. The flowrate, or flux, of hydrogen throughmembrane 46 typically is accelerated by providing a pressuredifferential between a mixed gaseous mixture on one side of themembrane, and the side of the membrane to which hydrogen migrates, withthe mixture side of the membrane being at a higher pressure than theother side.

Because of their extremely thin construction, membranes 46 typically aresupported by at least one of a support or frame. Frames, or framemembers, may be used to support the membranes from the perimeter regionsof the membranes. Supports, or support assemblies, typically support themembranes by extending across and in contact with at least a substantialportion of one or more of the membrane surfaces, such as surfaces 2 or19. By referring briefly back to FIG. 3, an illustrative example of aframe, or frame member, is shown and generally indicated at 15. Frame 15is secured to a membrane 46, such as around a portion or the entire edgeregion 6. Frame 15 is formed from a more durable material than themembrane and provides a support structure for the membrane. Frame 15 maybe secured to one or both surfaces of the membrane. It should beunderstood that the invented membrane may be formed without frame 15. Inanother variation, frame 15 may take the form of a compressible gasketthat is secured to the membrane, such as with an adhesive or othersuitable structure or process. Compressible gaskets are used to formgas-tight seals around and/or between the membranes.

In FIG. 9, illustrative examples of suitable configurations formembranes 46 are shown. As shown, membrane 46 includes a mixed-gassurface 48 which is oriented for contact by mixed gas stream 24, and apermeate surface 50, which is generally opposed to surface 48. Alsoshown at 52 are schematic representations of mounts, which may be anysuitable structure for supporting and/or positioning the membranes orother separation assemblies within compartment 18. Mounts 52 may includeor be at least partially formed from frames 15. Alternatively, mounts 52may be adapted to be coupled to frame 15 to selectively position themembrane within device 10. The patent and patent applicationsincorporated immediately above also disclose illustrative examples ofsuitable mounts 52. At 46′, membrane 46 is illustrated as a foil orfilm. At 46″, the membrane is supported by an underlying support 54,such as a mesh or expanded metal screen or a ceramic or other porousmaterial. At 46′″, the membrane is coated or formed onto or otherwisebonded to a porous member 56. It should be understood that the membraneconfigurations discussed above have been illustrated schematically inFIG. 9 and are not intended to represent every possible configurationwithin the scope of the disclosure.

Supports 54, frames 15 and mounts 52 should be thermally and chemicallystable under the operating conditions of device 10, and support 54should be sufficiently porous or contain sufficient voids to allowhydrogen that permeates membrane 46 to pass substantially unimpededthrough the support layer. Examples of support layer materials includemetal, carbon, and ceramic foam, porous and microporous ceramics, porousand microporous metals, metal mesh, perforated metal, and slotted metal.Additional examples include woven metal mesh (also known as screen) andtubular metal tension springs.

In embodiments of the disclosure in which membrane 46 is a metalmembrane and the support and/or frame also are formed from metal, it ispreferable that the support or frame is composed of metal that is formedfrom a corrosion-resistant material. Examples of such materials includecorrosion-resistant alloys, such as stainless steels and non-ferrouscorrosion-resistant alloys comprised of one or more of the followingmetals: chromium, nickel, titanium, niobium, vanadium, zirconium,tantalum, molybdenum, tungsten, silicon, and aluminum. Thesecorrosion-resistant alloys have a native surface oxide layer that ischemically and physically very stable and serves to significantly retardthe rate of intermetallic diffusion between the thin metal membrane andthe metal support layer. Such intermetallic diffusion, if it were tooccur, often results in degradation of the hydrogen permeability of themembrane and is undesirable.

Although membrane 46 is illustrated in FIG. 9 as having a planarconfiguration, it is within the scope of the disclosure that membrane 46may have non-planar configurations as well. For example, the shape ofthe membrane may be defined at least in part by the shape of a support54 or member 56 upon which the membrane is supported and/or formed. Assuch, membranes 46 may have concave, convex or other non-planarconfigurations, especially when device 10 is operating at an elevatedpressure. As another example, membrane 46 may have a tubularconfiguration, such as shown in FIGS. 10 and 11.

In FIG. 10, an example of a tubular membrane is shown in which the mixedgas stream is delivered to the interior of the membrane tube. In thisconfiguration, the interior of the membrane tube defines region 30 ofthe internal compartment, and the permeate region 32 of the compartmentlies external the tube. An additional membrane tube is shown in dashedlines in FIG. 10 to represent graphically that it is within the scope ofthe present disclosure that device 10 may include more than one membraneand/or more than one mixed-gas surface 48. It is within the scope of thedisclosure that device 10 may also include more than two membranes, andthat the relative spacing and/or configuration of the membranes mayvary.

In FIG. 1, another example of a hydrogen purification device 10 thatincludes tubular membranes is shown. In this illustrated configuration,device 10 is configured so that the mixed gas stream is delivered intocompartment 18 external to the membrane tube or tubes. In such aconfiguration, the mixed-gas surface of a membrane tube is exterior tothe corresponding permeate surface, and the permeate region is locatedinternal the membrane tube or tubes.

The tubular membranes may have a variety of configurations andconstructions, such as those discussed above with respect to the planarmembranes shown in FIG. 9. For example, illustrative examples of variousmounts 52, supports 54 and porous members 56 are shown in FIGS. 10 and11, including a spring 58, which has been schematically illustrated. Itis further within the scope of the disclosure that, tubular membranesmay have a configuration other than the straight cylindrical tube shownin FIG. 10. Examples of other configurations include U-shaped tubes andspiral or helical tubes.

As discussed, enclosure 12 defines a pressurized compartment 18 in whichseparation assembly 20 is positioned. In the embodiments shown in FIGS.9-11, enclosure 12 includes a pair of end plates 60 that are joined by aperimeter shell 62. It should be understood that device 10 has beenschematically illustrated in FIGS. 9-11 to show representative examplesof the general components of the device without intending to be limitedto geometry, shape and size. For example, end plates 60 typically arethicker than the walls of perimeter shell 62, but this is not required.Similarly, the thickness of the end plates may be greater than, lessthan or the same as the distance between the end plates. As a furtherexample, the thickness of membrane 46 has been exaggerated for purposesof illustration.

In FIGS. 9-11, it can be seen that mixed gas stream 24 is delivered tocompartment 18 through an input port 64, hydrogen-rich (or permeate)stream 34 is removed from device 10 through one or more product ports66, and the byproduct stream is removed from device 10 through one ormore byproduct ports 68. In FIG. 9, the ports are shown extendingthrough various ones of the end plates to illustrate that the particularlocation on enclosure 12 from which the gas streams are delivered to andremoved from device 10 may vary. It is also within the scope of thedisclosure that one or more of the streams may be delivered or withdrawnthrough shell 62, such as illustrated in dashed lines in FIG. 10. It isfurther within the scope of the invention that ports 64-68 may includeor be associated with flow-regulating and/or coupling structures.Examples of these structures include one or more of valves, flow andpressure regulators, connectors or other fittings and/or manifoldassemblies that are configured to permanently or selectively fluidlyinterconnect device 10 with upstream and downstream components. Forpurposes of illustration, these flow-regulating and/or couplingstructures are generally indicated at 70 in FIG. 9. For purposes ofbrevity, structures 70 have not been illustrated in every embodiment.Instead, it should be understood that some or all of the ports for aparticular embodiment of device 10 may include any or all of thesestructures, that each port does not need to have the same, if any,structure 70, and that two or more ports may in some embodiments shareor collectively utilize structure 70, such as a common collection ordelivery manifold, pressure relief valve, fluid-flow valve, etc.

Another illustrative example of a suitable configuration for an endplate 60 is shown in FIG. 10. As shown, plate 60 includes input, productand byproduct ports 64-68. Also shown in FIG. 10 is a heating conduit,or passage, 71 through which a stream 73 containing heat transferfluids, such as streams 24, 34 or 36, exhaust gases, etc., may be passedto selectively heat plate 60 and thereby decrease the heatingrequirements compared to a similarly sized end plate that is formed froma comparable solid slab of material. Especially when passage 71 isadapted to receive a fluid stream 73 other than one of streams 24 and34, it is preferable that the passage be isolated relative to ports64-68. In operation, hot (exhaust) gas passing through plate 60 elevatesthe temperature of a device that includes plate 60 and thereby reducesthe comparative time required to heat the device during start up. Ofcourse, it is within the scope of the disclosure that devices and/or endplates according to the present disclosure may be formed without passage71. Similarly, it is also within the scope of the disclosure that device10 may include more than one passage 71, and that the passage(s) mayextend through more than one region of enclosure 12, including shell 62.

End plates 60 and perimeter shell 62 are secured together by a retentionstructure 72. Structure 72 may take any suitable form capable ofmaintaining the components of enclosure 12 together in a fluid-tight orsubstantially fluid-tight configuration in the operating parameters andconditions in which device 10 is used. Examples of suitable structures72 include welds 74 and bolts 76, such as shown in FIGS. 9 and 11. InFIG. 11, bolts 76 are shown extending through flanges 78 that extendfrom the components of enclosure 12 to be joined. In FIG. 12, bolts 76are shown extending through compartment 18. It should be understood thatthe number of bolts may vary, and typically will include a plurality ofbolts or similar fastening mechanisms extending around the perimeter ofenclosure 18. Bolts 76 should be selected to be able to withstand theoperating parameters and conditions of device 10, including the tensionimparted to the bolts when device 10 is pressurized.

In the lower halves of FIGS. 11 and 12, gaskets 80 are shown toillustrate that enclosure 12 may, but does not necessarily, include aseal member 82 interconnecting or spanning the surfaces to be joined toenhance the leak-resistance of the enclosure. The seal member should beselected to reduce or eliminate leaks when used at the operatingparameters and under the operating conditions of the device. Therefore,in many embodiments, high-pressure and/or high-temperature seals shouldbe selected. An illustrative, non-exclusive example of such a sealstructure is a graphite gasket, such as sold by Union Carbide under thetrade name GRAFOIL™. As used herein, “seal member” and “sealing member”are meant to refer to structures or materials applied to, placedbetween, or placed in contact with the metallic end plates and shell (orshell portions) to enhance the seal established therebetween. Gaskets orother sealing members may also be used internal compartment 18, such asto provide seals between adjacent membranes, fluid conduits, mounts orsupports, and/or any of the above with the internal surface of enclosure12.

In FIGS. 9 and 11-12, the illustrated enclosures include a pair of endplates 60 and a shell 62. With reference to FIG. 12, it can be seen thatthe end plates include sealing regions 90, which form an interface 94with a corresponding sealing region 92 of shell 62. In many embodiments,the sealing region of end plate 60 will be a perimeter region, and assuch, sealing region 90 will often be referred to herein as a perimeterregion 90 of the end plate. However, as used herein, the perimeterregion is meant to refer to the region of the end plate that extendsgenerally around the central region and which forms an interface with aportion of the shell, even if there are additional portions or edges ofthe end plate that project beyond this perimeter portion. Similarly,sealing region 92 of shell 62 will typically be an end region of theshell. Accordingly, the sealing region of the shell will often bereferred to herein as end region 92 of the shell. It is within the scopeof the disclosure, however, that end plates 60 may have portions thatproject outwardly beyond the sealing region 90 and interface 94 formedwith shell 62, and that shell 62 may have regions that project beyondend plate 60 and the interface formed therewith. These portions areillustrated in dashed lines in FIG. 12 at 91 and 93 for purposes ofgraphical illustration.

As an alternative to a pair of end plates 60 joined by a separateperimeter shell 62, enclosure 12 may include a shell that is at leastpartially integrated with either or both of the end plates. For example,in FIG. 13, a portion 63 of shell 62 is integrally formed with each endplate 60. Described another way, each end plate 60 includes shellportions, or collars, 63 that extend from the perimeter region 90 of theend plate. As shown, the shell portions include end regions 92 whichintersect at an interface 94. In the illustrated embodiment, the endregions abut each other without a region of overlap; however, it iswithin the scope of the disclosure that interface 94 may have otherconfigurations, such as those illustrated and/or described subsequently.End regions 92 are secured together via any suitable mechanism, such asby any of the previously discussed retention structures 72, and may (butdo not necessarily) include a seal member 82 in addition to the matingsurfaces of end regions 92.

A benefit of shell 62 being integrally formed with at least one of theend plates is that the enclosure has one less interface that must besealed. This benefit may be realized by reduced leaks due to the reducednumber of seals that could fail, fewer components, and/or a reducedassembly time for device 10. Another example of such a construction forenclosure 12 is shown in FIG. 13, in which shell 62 is integrally formedwith one of the end plates, with a shell portion 63 that extendsintegrally from the perimeter region 90 of one of the end plates. Shellportion 63 includes an end region 92 that forms an interface 94 with theperimeter region 90 of the other end plate via any suitable retentionstructure 72, such as those described above. The combined end plate andshell components shown in FIGS. 13 and 14 may be formed via any suitablemechanism, including machining them from a solid bar or block ofmaterial. For purposes of simplicity, separation assembly 20 and theinput and output ports have not been illustrated in FIGS. 13 and 14 andonly illustrative, non-exclusive examples of suitable retentionstructure 72 are shown. Similar to the other enclosures illustrated anddescribed herein, it should be understood that the relative dimensionsof the enclosure may vary and still be within the scope of thedisclosure. For example, shell portions 63 may have lengths that arelonger or shorter than those illustrated in FIGS. 13 and 14.

Before proceeding to additional illustrative configurations for endplates 60, it should be clarified that as used herein in connection withthe enclosures of devices 10, the term “interface” is meant to refer tothe interconnection and sealing region that extends between the portionsof enclosure 12 that are separately formed and thereafter securedtogether, such as (but not necessarily) by one of the previouslydiscussed retention structures 72. The specific geometry and size ofinterface 94 will tend to vary, such as depending upon size,configuration and nature of the components being joined together.Therefore, interface 94 may include a metal-on-metal seal formed betweencorresponding end regions and perimeter regions, a metal-on-metal sealformed between corresponding pairs of end regions, a metal-gasket (orother seal member 82)-metal seal, etc. Similarly, the interface may havea variety of shapes, including linear, arcuate and rectilinearconfigurations that are largely defined by the shape and relativeposition of the components being joined together.

For example, in FIG. 14, an interface 94 extends between end region 92of shell portion 63 and perimeter region 90 of end plate 60. As shown,regions 90 and 92 intersect with parallel edges. As discussed, a gasketor other seal member may extend between these edges. In FIGS. 15-18,nonexclusive examples of additional interfaces 94 that are within thescope of the disclosure are shown. Embodiments of enclosure 12 thatinclude an interface 94 formed between adjacent shell regions may alsohave any of these configurations. In FIG. 15, perimeter region 90defines a recess or corner into which end region 92 of shell 62 extendsto form an interface 94 that extends around this corner. Also shown inFIG. 15 is central region 96 of end plate 60, which as illustratedextends within shell 62 and defines a region of overlap therewith.

In FIG. 16, perimeter region 90 defines a corner that opens generallytoward compartment 18, as opposed to the corner of FIG. 15, which opensgenerally away from compartment 18. In the configuration shown in FIG.16, perimeter region 90 includes a collar portion 98 that extends atleast partially along the outer surface 100 of shell 62 to define aregion of overlap therewith. Central region 96 of plate 60 is shown insolid lines extending along end region 92 without extending into shell62, in dashed lines extending into shell 62, and in dash-dot linesincluding an internal support 102 that extends at least partially alongthe inner surface 104 of shell 62. FIGS. 17 and 18 are similar to FIGS.15 and 16 except that perimeter region 90 and end region 92 are adaptedto threadingly engage each other, and accordingly include correspondingthreads 106 and 108. In dashed lines in FIG. 17, an additional exampleof a suitable configuration for perimeter region 90 of end plate 60 isshown. As shown, the outer edge 110 of the end plate does not extendradially (or outwardly) to or beyond the exterior surface of shell 62.

It should be understood that any of these interfaces may be used with anenclosure constructed according to the present disclosure. However, forpurposes of brevity, every embodiment of enclosure 12 will not be shownwith each of these interfaces. Although somewhat schematicallyillustrated in the previously discussed figures, it should be understoodthat embodiments of device 10 that include end plates 60 may include endplates having a variety of configurations, such as those disclosed inthe patent applications incorporated herein. Therefore, although thesubsequently described end plates shown in FIGS. 19-26 are shown withthe interface configuration of FIG. 15, it is within the scope of thedisclosure that the end plates and corresponding shells may beconfigured to have any of the interfaces described and/or illustratedherein, as well as the integrated shell configuration described andillustrated with respect to FIGS. 13 and 14. Similarly, it should beunderstood that the devices constructed according to the presentdisclosure may have any of the enclosure configurations, interfaceconfigurations, retention structure configurations, separation assemblyconfigurations, flow-regulating and/or coupling structures, seal memberconfigurations, and port configurations discussed, described and/orincorporated herein. Illustrative examples of suitable end plateconfigurations are shown in FIGS. 19-32. Although the following endplate configurations are illustrated with circular perimeters, it iswithin the scope of the disclosure that the end plates may be configuredto have perimeters with any other geometric configuration, includingarcuate, rectilinear, and angular configurations, as well ascombinations thereof.

Consider for example a circular end plate formed from Type 304 stainlesssteel and having a uniform thickness of 0.75 inches. Such an end plateweights 7.5 pounds. A hydrogen purification device containing this endplate was exposed to operating parameters of 400° C. and 175 psi.Maximum stresses of 25,900 psi were imparted to the end plate, with amaximum deflection of 0.0042 inches and a deflection at perimeter region90 of 0.0025 inches.

Another end plate 60 constructed according to the present disclosure isshown in FIGS. 19 and 20 and generally indicated at 120. As shown, endplate 120 has interior and exterior surfaces 122 and 124. Interiorsurface 122 includes central region 96 and perimeter region 90. Exteriorsurface 124 has a central region 126 and a perimeter region 128, and inthe illustrated embodiment, plate 120 has a perimeter 130 extendingbetween the perimeter regions 90 and 128 of the interior and exteriorsurfaces. As discussed above, perimeter region 90 may have any of theconfigurations illustrated or described above, including a configurationin which the sealing region is at least partially or completely locatedalong perimeter 130. In the illustrated embodiment, perimeter 130 has acircular configuration. However, it is within the scope of thedisclosure that the shape may vary, such as to include rectilinear andother arcuate, geometric, linear, and/or cornered configurations.

Unlike the previously illustrated end plates, however, the centralregion of the end plate has a variable thickness between its interiorand exterior surfaces, which is perhaps best seen in FIG. 20. Unlike auniform slab of material, the exterior surface of plate 120 has acentral region 126 that includes an exterior cavity, or removed region,132 that extends into the plate and generally toward central region 96on interior surface 122. Described another way, the end plate has anonplanar exterior surface, and more specifically, an exterior surfacein which at least a portion of the central region extends toward thecorresponding central region of the end plate's interior surface. Region132 reduces the overall weight of the end plate compared to a similarlyconstructed end plate that does not include region 132. As used herein,removed region 132 is meant to exclude ports or other bores that extendcompletely through the end plates. Instead, region 132 extends into, butnot through, the end plate.

A reduction in weight means that a purification device 10 that includesthe end plate will be lighter than a corresponding purification devicethat includes a similarly constructed end plate formed without region132. With the reduction in weight also comes a corresponding reductionin the amount of heat (thermal energy) that must be applied to the endplate to heat the end plate to a selected operating temperature. In theillustrated embodiment, region 132 also increases the surface area ofexterior surface 124. Increasing the surface area of the end platecompared to a corresponding end plate may, but does not necessarily inall embodiments, increase the heat transfer surface of the end plate,which in turn, can reduce the heating requirements and/or time of adevice containing end plate 120.

In some embodiments, plate 120 may also be described as having a cavitythat corresponds to, or includes, the region of maximum stress on asimilarly constructed end plate in which the cavity was not present.Accordingly, when exposed to the same operating parameters andconditions, lower stresses will be imparted to end plate 120 than to asolid end plate formed without region 132. For example, in the solid endplate with a uniform thickness, the region of maximum stress occurswithin the portion of the end plate occupied by removed region 132 inend plate 120. Accordingly, an end plate with region 132 mayadditionally or alternatively be described as having a stress abatementstructure 134 in that an area of maximum stress that would otherwise beimparted to the end plate has been removed.

For purposes of comparison, consider an end plate 120 having theconfiguration shown in FIGS. 19 and 20, formed from Type 304 stainlesssteel, and having a diameter of 6.5 inches. This configurationcorresponds to maximum plate thickness of 0.75 inches and a removedregion 132 having a length and width of 3 inches. When utilized in adevice 10 operating at 400° C. and 175 psi, plate 120 has a maximumstress imparted to it of 36,000 psi, a maximum deflection of 0.0078inches, a displacement of 0.0055 inches at perimeter region 90, and aweight of 5.7 pounds. It should be understood that the dimensions andproperties described above are meant to provide an illustrative exampleof the combinations of weight, stress and displacement experienced byend plates according to the present disclosure, and that the specificperimeter shape, materials of construction, perimeter size, thickness,removed region shape, removed region depth and removed region perimeterall may vary within the scope of the disclosure.

In FIG. 19, it can be seen that region 132 (and/or stress abatementstructure 134) has a generally square or rectilinear configurationmeasured transverse to surfaces 122 and 124. As discussed, othergeometries and dimensions may be used and are within the scope of thedisclosure. To illustrate this point, variations of end plate 120 areshown in FIGS. 21 and 22 and generally indicated at 120′. In thesefigures, region 132 is shown having a circular perimeter. It should beunderstood that the relative dimensions of region 132 compared to therest of the end plate may vary, such as being either larger or smallerthan shown in FIGS. 21 and 22.

For purposes of comparison, consider an end plate 120 having theconfiguration shown in FIGS. 21 and 22 and having the same materials ofconstruction, perimeter and thickness as the end plate shown in FIGS. 19and 20. Instead of the generally square removed region of FIGS. 19 and20, however, end plate 120′ has a removed region with a generallycircular perimeter and a diameter of 3.25 inches. End plate 120′ weighsthe same as end plate 120, but has reduced maximum stress anddeflections. More specifically, while end plate 120 had a maximum stressgreater than 35,000 psi, end plate 120′ had a maximum stress that isless than 30,000 psi, and in the illustrated configuration less than25,000 psi, when subjected to the operating parameters discussed abovewith respect to plate 120. In fact, plate 120′ demonstratedapproximately a 35% reduction in maximum stress compared to plate 120.The maximum and perimeter region deflections of plate 120′ were alsoless than plate 120, with a measured maximum deflection of 0.007 inchesand a measured deflection at perimeter region 90 of 0.0050 inches.

As a further example, forming plate 120′ with a region 132 having adiameter of 3.75 inches instead of 3.25 inches decreases the weight ofthe end plate to 5.3 pounds and produced the same maximum deflection.This variation produces a maximum stress that is less than 25,000 psi,although approximately 5% greater than that of end plate 120′ (24,700psi, compared to 23,500 psi). At perimeter region 90, this variation ofend plate 120′ exhibited a maximum deflection of 0.0068 inches.

In FIGS. 19-23, illustrative port configurations have been shown. InFIGS. 21 and 22, a port 138 is shown in dashed lines extending frominterior surface 122 through the end plate to exterior surface 124.Accordingly, with such a configuration a gas stream is delivered orremoved via the exterior surface of the end plate of device 10. In sucha configuration, fluid conduits and/or flow-regulating and/or couplingstructure 70 typically will project from the exterior surface 124 of theend plate. Another suitable configuration is indicated at 140 in dashedlines in FIGS. 19 and 20. As shown, port 140 extends from the interiorsurface of the end plate, and then through perimeter 130 instead ofexterior surface 124. Accordingly, port 140 enables gas to be deliveredor removed from the perimeter of the end plate instead of the exteriorsurface of the end plate. It should be understood that ports 64-68 mayhave these configurations illustrated by ports 138 and 140. Of course,ports 64-68 may have any other suitable port configuration as well,including a port that extends through shell 62 or a shell portion. Forpurposes of simplicity, ports will not be illustrated in many of thesubsequently described end plates, just as they were not illustrated inFIGS. 13 and 14.

Also shown in dashed lines in FIGS. 19 and 21-22 are guide structures144. Guide structures 144 extend into compartment 18 and providesupports that may be used to position and/or align separation assembly20, such as membranes 46. In some embodiments, guide structures 144 maythemselves form mounts 52 for the separation assembly. In otherembodiments, the device includes mounts other than guide structures 144.Guide structures may be used with any of the end plates illustrated,incorporated and/or described herein, regardless of whether any suchguide structures are shown in a particular drawing figure. However, itshould also be understood that hydrogen purification devices accordingto the present disclosure may be formed without guide structures 144. Inembodiments of device 10 that include guide structures 144 that extendinto or through compartment 18, the number of such structures may varyfrom a single support to two or more supports. Similarly, while guidestructures 144 have been illustrated as cylindrical ribs or projections,other shapes and configurations may be used within the scope of thedisclosure.

Guide structures 144 may be formed from the same materials as thecorresponding end plates. Additionally or alternatively, the guidestructures may include a coating or layer of a different material. Guidestructures 144 may be either separately formed from the end plates andsubsequently attached thereto, or integrally formed therewith. Guidestructures 144 may be coupled to the end plates by any suitablemechanism, including attaching the guide structures to the interiorsurfaces of the end plates, inserting the guide structures into boresextending partially through the end plates from the interior surfacesthereof, or inserting the guide structures through bores that extendcompletely through the end plates. In embodiments where the end platesinclude bores that extend completely through the end plates (which aregraphically illustrated for purposes of illustration at 146 in FIG. 22),the guide structures may be subsequently affixed to the end plates.Alternatively, the guide structures may be inserted through compartment18 until the separation assembly is properly assigned and securedtherein, and then the guide structures may be removed and the boressealed (such as by welding) to prevent leaks.

In FIGS. 23 and 24, another illustrative example of a suitableconfiguration for end plate 60 is shown and generally indicated at 150.Unless otherwise specified, it should be understood that end plates 150may have any of the elements, subelements and variations as any of theother end plates shown, described and/or incorporated herein. Similar toend plate 120′, plate 150 includes an exterior surface 124 with aremoved region 132 (and/or stress abatement structure 134) having acircular perimeter with a diameter of 3.25 inches. Exterior surface 124further includes an outer removed region 152 that extends from centralregion 126 to perimeter portion 128. Outer removed region 152 decreasesin thickness as it approaches perimeter 130. In the illustratedembodiment, region 152 has a generally linear reduction in thickness,although other linear and arcuate transitions may be used.

For purposes of comparison, end plate 150 has a reduced weight comparedto end plates 120 and 120′. Plate 150 weighed 4.7 pounds and experiencedmaximum stresses of 25,000 psi or less when subjected to the operatingparameters discussed above (400° C. and 175 psi). The maximum deflectionof the plate was 0.0098 inches, and the displacement at perimeter region90 was 0.0061 inches.

Another illustrative example of a suitable configuration for end plate60 is shown in FIGS. 25 and 26 and generally indicated at 160. Unlessotherwise specified, end plate 160 may have the same elements,subelements and variations as the other end plates illustrated,described and/or incorporated herein. End plate 160 may be referred toas a truss-stiffened end plate because it includes a truss assembly 162that extends from the end plate's exterior surface 124. As shown, endplate 160 has a base plate 164 with a generally planar configuration,similar to the end plates shown in FIGS. 9 and 11-13. However, trussassembly 162 enables, but does not require, that the base plate may havea thinner construction while still providing comparable if not reducedmaximum stresses and deflections. It is within the scope of thedisclosure that any of the other end plates illustrated, describedand/or incorporated herein also may include a truss assembly 162.

Truss assembly 162 extends from exterior surface 124 of base plate 164and includes a plurality of projecting ribs 166 that extend fromexterior surface 124. In FIGS. 25 and 26, it can be seen that ribs 166are radially spaced around surface 124. Nine ribs 166 are shown in FIGS.21 and 23, but it is within the scope of the disclosure that trussassembly 162 may be formed with more or fewer ribs. Similarly, in theillustrated embodiment, ribs 166 have arcuate configurations, andinclude flanges 168 extending between the ribs and surface 124. Flanges168 may also be described as heat transfer fins because they addconsiderable heat transfer area to the end plate. Truss assembly 162further includes a tension collar 170 that interconnects the ribs. Asshown, collar 170 extends generally parallel to surface base plate 164and has an open central region 172. Collar 170 may be formed with aclosed or internally or externally projecting central portion withoutdeparting from the disclosure. To illustrate this point, members 174 areshown in dashed lines extending across collar 170 in FIG. 21. Similarly,collar 170 may have configurations other than the circular configurationshown in FIGS. 25 and 26. As a further alternative, base plate 164 hasbeen indicated in partial dashed lines in FIG. 26 to graphicallyillustrate that the base plate may have a variety of configurations,such as those described, illustrated and incorporated herein, includingthe configuration shown if the dashed region is removed.

End plate 160 may additionally, or alternatively, be described as havinga support (170) that extends in a spaced-apart relationship beyondexterior surface 124 of base plate 164 and which is adapted to provideadditional stiffness and/or strength to the base plate. Still anotheradditional or alternative description of end plate 160 is that the endplate includes heat transfer structure (162) extending away from theexterior surface of the base plate, and that the heat transfer structureincludes a surface (170) that is spaced-away from surface 124 such thata heated fluid stream may pass between the surfaces.

Truss assembly 162 may also be referred to as an example of a deflectionabatement structure because it reduces the deflection that wouldotherwise occur if base plate 164 were formed without the trussassembly. Similarly, truss assembly 162 may also provide another exampleof a stress abatement restructure because it reduces the maximumstresses that would otherwise be imparted to the base plate.Furthermore, the open design of the truss assembly increases the heattransfer area of the base plate without adding significant weight to thebase plate.

Continuing the preceding comparisons between end plates, plate 160 wassubjected to the same operating parameters as the previously describedend plates. The maximum stresses imparted to base plate 164 were 10,000psi or less. Similarly, the maximum deflection of the base plate wasonly 0.0061 inches, with a deflection of 0.0056 inches at perimeterregion 90. It should be noted, that base plate 160 achieved thissignificant reduction in maximum stress while weighing only 3.3 pounds.Similarly, base plate 164 experienced a smaller maximum displacement andcomparable or reduced perimeter displacement yet had a base plate thatwas only 0.25 inches thick. Of course, plate 160 may be constructed withthicker base plates, but the tested plate proved to be sufficientlystrong and rigid under the operating parameters with which it was used.

As discussed, enclosure 12 may include a pair of end plates 60 and aperimeter shell. In FIG. 27, an example of an enclosure 12 formed with apair of end plates 160 is shown for purposes of illustration andindicated generally at 180. Although enclosure 180 has a pair oftruss-stiffened end plates 160, it is within the scope of the disclosurethat an enclosure may have end plates having different constructionsand/or configurations. In fact, in some operating environments it may bebeneficial to form enclosure 12 with two different types of end plates.In others, it may be beneficial for the end plates to have the sameconstruction.

In FIGS. 28 and 29 another example of an enclosure 12 is shown andgenerally indicated at 190 and includes end plates 120′″. End plates120′″ have a configuration similar to FIGS. 21 and 22, except removedregion 132 is shown having a diameter of 4 inches to further illustratethat the shape and size of the removed region may vary within the scopeof the disclosure. Both end plates include shell portions 63 extendingintegrally therefrom to illustrate that any of the end platesillustrated, described, and/or incorporated herein may include a shellportion 63 extending integrally therefrom. To illustrate that any of theend plates described, illustrated and/or incorporated herein may alsoinclude truss assemblies (or heat transfer structure) 162 and/orprojecting supports 170 or deflection abatement structure, members 194are shown projecting across removed region 132 in a spaced-apartconfiguration from the exterior surface 124 of the end plate.

It is also within the scope of the disclosure that enclosure 12 mayinclude stress and/or deflection abatement structures that extend intocompartment 18 as opposed to, or in addition to, correspondingstructures that extend from the exterior surface of the end plates. InFIGS. 30-32, end plates 60 are shown illustrating examples of thesestructures. For example, in FIG. 30, end plate 60 includes a removedregion 132 that extends into the end plate from the interior surface 122of the end plate. It should be understood that region 132 may have anyof the configurations described, illustrated and/or incorporated hereinwith respect to removed regions that extend from the exterior surface ofa base plate. Similarly, in dashed lines at 170 in FIG. 30, supports areshown extending across region 132 to provide additional support and/orrigidity to the end plate. In FIG. 31, end plate 60 includes internalsupports 196 that are adapted to extend into compartment 18 tointerconnect the end plate with the corresponding end plate at the otherend of the compartment. As discussed, guide structures 144 may form sucha support. In FIG. 32, an internally projecting truss assembly 162 isshown.

As discussed, the dimensions of device 10 and enclosure 12 may alsovary. For example, an enclosure designed to house tubular separationmembranes may need to be longer (i.e. have a greater distance betweenend plates) than an enclosure designed to house planar separationmembranes to provide a comparable amount of membrane surface areaexposed to the mixed gas stream (i.e., the same amount of effectivemembrane surface area). Similarly, an enclosure configured to houseplanar separation membranes may tend to be wider (i.e., have a greatercross-sectional area measured generally parallel to the end plates) thanan enclosure designed to house tubular separation membranes. However, itshould be understood that neither of these relationships are required,and that the specific size of the device and/or enclosure may vary.Factors that may affect the specific size of the enclosure include thetype and size of separation assembly to be housed, the operatingparameters in which the device will be used, the flow rate of mixed gasstream 24, the shape and configuration of devices such as heatingassemblies, fuel processors and the like with which or within which thedevice will be used, and to some degree, user preferences.

As discussed previously, hydrogen purification devices may be operatedat elevated temperatures and/or pressures. Both of these operatingparameters may impact the design of enclosures 12 and other componentsof the devices. For example, consider a hydrogen purification device 10operated at a selected operating temperature above an ambienttemperature, such as a device operating at 400° C. As an initial matter,the device, including enclosure 12 and separation assembly 20, must beconstructed from a material that can withstand the selected operatingtemperature, and especially over prolonged periods of time and/or withrepeated heating and cooling off cycles. Similarly, the materials thatare exposed to the gas streams preferably are not reactive or at leastnot detrimentally reactive with the gases. An example of a suitablematerial is stainless steel, such as Type 304 stainless steel, althoughothers may be used.

Besides the thermal and reactive stability described above, operatingdevice 10 at a selected elevated temperature requires one or moreheating assemblies 42 to heat the device to the selected operatingtemperature. When the device is initially operated from a shutdown, orunheated, state, there will be an initial startup or preheating periodin which the device is heated to the selected operating temperature.During this period, the device may not produce a hydrogen-rich stream atall, a hydrogen-rich stream that contains more than an acceptable levelof the other gases, and/or a reduced flow rate of the hydrogen-richstream compared to the byproduct stream or streams (meaning that agreater percentage of the hydrogen gas is being exhausted as byproductinstead of product). In addition to the time to heat the device, onemust also consider the heat or thermal energy required to heat thedevice to the selected temperature. The heating assembly or assembliesmay add to the operating cost, materials cost, and/or equipment cost ofthe device. For example, a simplified end plate 60 is a relatively thickslab having a uniform thickness. In fact, stainless steel plates havinga uniform thickness of 0.5 inches or 0.75 inches have proven effectiveto support and withstand the operating parameters and conditions ofdevice 10. However, the dimensions of these plates add considerableweight to device 10, and in many embodiments require considerablethermal energy to be heated to the selected operating temperature. Asused herein, the term “uniform thickness” is meant to refer to devicesthat have a constant or at least substantially constant thickness,including those that deviate in thickness by a few percent (less than5%) along their lengths. In contrast, and as used herein, a “variablethickness” will refer to a thickness that varies by at least 10%, and insome embodiments at least 25%, 40% or 50%.

The pressure at which device 10 is operated may also affect the designof device 10, including enclosure 12 and separation assembly 20.Consider for example a device operating at a selected pressure of 175psi. Device 10 must be constructed to be able to withstand the stressesencountered when operating at the selected pressure. This strengthrequirement affects not only the seals formed between the components ofenclosure 12, but also the stresses imparted to the componentsthemselves. For example, deflection or other deformation of the endplates and/or shell may cause gases within compartment 18 to leak fromthe enclosure. Similarly, deflection and/or deformation of thecomponents of the device may also cause unintentional mixing of two ormore of gas streams 24, 34 and 36. For example, an end plate may deformplastically or elastically when subjected to the operating parametersunder which device 10 is used. Plastic deformation results in apermanent deformation of the end plate, the disadvantage of whichappears fairly evident. Elastic deformation, however, also may impairthe operation of the device because the deformation may result ininternal and/or external leaks. More specifically, the deformation ofthe end plates or other components of enclosure 12 may enable gases topass through regions where fluid-tight seals previously existed. Asdiscussed, device 10 may include gaskets or other seal members to reducethe tendency of these seals to leak, however, the gaskets have a finitesize within which they can effectively prevent or limit leaks betweenopposing surfaces. For example, internal leaks may occur in embodimentsthat include one or more membrane envelopes or membrane platescompressed (with or without gaskets) between the end plates. As the endplates deform and deflect away from each other, the plates and/orgaskets may in those regions not be under the same tension orcompression as existed prior to the deformation. Gaskets, or gasketplates, may be located between a membrane envelope and adjacent feedplates, end plates, and/or other adjacent membrane envelopes. Similarly,gaskets or gasket plates may also be positioned within a membraneenvelope to provide additional leak prevention within the envelope.

In view of the above, it can be seen that there are several competingfactors to be weighed with respect to device 10. In the context ofenclosure 12, the heating requirements of the enclosure will tend toincrease as the materials used to form the enclosure are thickened. Tosome degree using thicker materials may increase the strength of theenclosure, however, it may also increase the heating and materialrequirements, and in some embodiments actually produce regions to whichgreater stresses are imparted compared to a thinner enclosure. Areas tomonitor on an end plate include the deflection of the end plate,especially at the perimeter regions that form interface(s) 94, and thestresses imparted to the end plate.

As discussed, enclosure 12 contains an internal compartment 18 thathouses separation assembly 20, such as one or more separation membranes46, which are supported within the enclosure by a suitable mount 52. Inthe illustrative examples shown in FIGS. 9 and 12, the separationmembranes 46 are depicted as independent planar or tubular membranes. Itis also within the scope of the disclosure that the membranes may bearranged in pairs that define permeate region 32 therebetween. In such aconfiguration, the membrane pairs may be referred to as a membraneenvelope, in that they define a common permeate region 32 in the form ofa harvesting conduit, or flow path, extending therebetween and fromwhich hydrogen-rich stream 34 may be collected.

An example of a membrane envelope is shown in FIG. 33 and generallyindicated at 200. It should be understood that the membrane pairs maytake a variety of suitable shapes, such as planar envelopes and tubularenvelopes. Similarly, the membranes may be independently supported, suchas with respect to an end plate or around a central passage. Forpurposes of illustration, the following description and associatedillustrations will describe the separation assembly as including one ormore membrane envelopes 200. It should be understood that the membranesforming the envelope may be two separate membranes, or may be a singlemembrane folded, rolled or otherwise configured to define two membraneregions, or surfaces, 202 with permeate surfaces 50 that are orientedtoward each other to define a conduit 204 therebetween from which thehydrogen-rich permeate gas may be collected and withdrawn. Conduit 204may itself form permeate region 32, or a device 10 according to thepresent disclosure may include a plurality of membrane envelopes 200 andcorresponding conduits 204 that collectively define permeate region 32.Furthermore, membranes 46 may have any of the compositions andstructures described and incorporated herein.

As discussed, a support 54 may be used to support the membranes againsthigh feed pressures. Support 54 should enable gas that permeates throughmembranes 46 to flow therethrough. Support 54 includes surfaces 211against which the permeate surfaces 50 of the membranes are supported.In the context of a pair of membranes forming a membrane envelope,support 54 may also be described as defining harvesting conduit 204. Inconduit 204, permeated gas preferably may flow both transverse andparallel to the surface of the membrane through which the gas passes,such as schematically illustrated in FIG. 33. The permeate gas, which isat least substantially pure hydrogen gas, may then be harvested orotherwise withdrawn from the envelope to form hydrogen-rich stream 34.Because the membranes lie against the support, it is preferable that thesupport does not obstruct the flow of gas through the hydrogen-selectivemembranes. The gas that does not pass through the membranes forms one ormore byproduct streams 36, as schematically illustrated in FIG. 33.

An example of a suitable support 54 for membrane envelopes 200 is shownin FIG. 34 in the form of a screen structure 210. Screen structure 210includes plural screen members 212. In the illustrated embodiment, thescreen members include a coarse mesh screen 214 sandwiched between finemesh screens 216. It should be understood that the terms “fine” and“coarse” are relative terms. Preferably, the outer screen members areselected to support membranes 46 without piercing the membranes andwithout having sufficient apertures, edges or other projections that maypierce, weaken or otherwise damage the membrane under the operatingconditions with which device 10 is operated. Because the screenstructure needs to provide for flow of the permeated gas generallyparallel to the membranes, it is preferable to use a relatively courserinner screen member to provide for enhanced, or larger, parallel flowconduits. In other words, the finer mesh screens provide betterprotection for the membranes, while the coarser mesh screen providesbetter flow generally parallel to the membranes.

The screen members may be of similar or the same construction, and moreor less screen members may be used than shown in FIG. 34. Preferably,support 54 is formed from a corrosion-resistant material that will notimpair the operation of the hydrogen purification device and otherdevices with which device 10 is used. Examples of suitable materials formetallic screen members include stainless steels, titanium and alloysthereof, zirconium and alloys thereof, corrosion-resistant alloys,including Inconel™ alloys, such as 800H™, and Hastelloy™ alloys, andalloys of copper and nickel, such as Monel™. Additional examples ofstructure for supports 54 include porous ceramics, porous carbon, porousmetal, ceramic foam, carbon foam, and metal foam, either alone, or incombination with one or more screen members 212. As another example,some or all of the screen members may be formed from expanded metalinstead of a woven mesh material.

During fabrication of the membrane envelopes, adhesive may be used tosecure membranes 46 to the screen structure and/or to secure thecomponents of screen structure 210 together, as discussed in more detailin the above-incorporated U.S. patent application Ser. No. 09/812,499.For purposes of illustration, adhesive is generally indicated in dashedlines at 218 in FIG. 34. An example of a suitable adhesive is sold by 3M under the trade name SUPER 77. Typically, the adhesive is at leastsubstantially, if not completely, removed after fabrication of themembrane envelope so as not to interfere with the permeability,selectivity and flow paths of the membrane envelopes. An example of asuitable method for removing adhesive from the membranes and/or screenstructures or other supports is by exposure to oxidizing conditionsprior to initial operation of device 10. The objective of the oxidativeconditioning is to burn out the adhesive without excessively oxidizingthe palladium-alloy membrane. A suitable procedure for such oxidizing isdisclosed in the above-incorporated patent application.

Supports 54, including screen structure 210, may include a coating 219on the surfaces 211 that engage membranes 46, such as indicated indash-dot lines in FIG. 34. Examples of suitable coatings includealuminum oxide, tungsten carbide, tungsten nitride, titanium carbide,titanium nitride, and mixtures thereof. These coatings are generallycharacterized as being thermodynamically stable with respect todecomposition in the presence of hydrogen. Suitable coatings are formedfrom materials, such as oxides, nitrides, carbides, or intermetalliccompounds, that can be applied as a coating and which arethermodynamically stable with respect to decomposition in the presenceof hydrogen under the operating parameters (temperature, pressure, etc.)under which the hydrogen purification device will be operated. Suitablemethods for applying such coatings to the screen or expanded metalscreen member include chemical vapor deposition, sputtering, thermalevaporation, thermal spraying, and, in the case of at least aluminumoxide, deposition of the metal (e.g., aluminum) followed by oxidation ofthe metal to give aluminum oxide. In at least some embodiments, thecoatings may be described as preventing intermetallic diffusion betweenthe hydrogen-selective membranes and the screen structure.

The hydrogen purification devices 10 described, illustrated and/orincorporated herein may include one or more membrane envelopes 200,typically along with suitable input and output ports through which themixed gas stream is delivered and from which the hydrogen-rich andbyproduct streams are removed. In some embodiments, the device mayinclude a plurality of membrane envelopes. When the separation assemblyincludes a plurality of membrane envelopes, it may include fluidconduits interconnecting the envelopes, such as to deliver a mixed gasstream thereto, to withdraw the hydrogen-rich stream therefrom, and/orto withdraw the gas that does not pass through the membranes from mixedgas region 30. When the device includes a plurality of membraneenvelopes, the permeate stream, byproduct stream, or both, from a firstmembrane envelope may be sent to another membrane envelope for furtherpurification. The envelope or plurality of envelopes and associatedports, supports, conduits and the like may be referred to as a membranemodule 220.

The number of membrane envelopes 200 used in a particular device 10depends to a degree upon the feed rate of mixed gas stream 24. Forexample, a membrane module 220 containing four envelopes 200 has proveneffective for a mixed gas stream delivered to device 10 at a flow rateof 20 liters/minute. As the flow rate is increased, the number ofmembrane envelopes may be increased, such as in a generally linearrelationship. For example, a device 10 adapted to receive mixed gasstream 24 at a flow rate of 30 liters/minute may preferably include sixmembrane envelopes. However, these exemplary numbers of envelopes areprovided for purposes of illustration, and greater or fewer numbers ofenvelopes may be used. For example, factors that may affect the numberof envelopes to be used include the hydrogen flux through the membranes,the effective surface area of the membranes, the flow rate of mixed gasstream 24, the desired purity of hydrogen-rich stream 34, the desiredefficiency at which hydrogen gas is removed from mixed gas stream 24,user preferences, the available dimensions of device 10 and compartment18, etc.

Preferably, but not necessarily, the screen structure and membranes thatare incorporated into a membrane envelope 200 include frame members 230,or plates, that are adapted to seal, support and/or interconnect themembrane envelopes. An illustrative example of suitable frame members230 is shown in FIG. 35. As shown, screen structure 210 fits within aframe member 230 in the form of a permeate frame 232. The screenstructure and frame 232 may collectively be referred to as a screenplate or permeate plate 234. When screen structure 210 includes expandedmetal members, the expanded metal screen members may either fit withinpermeate frame 232 or extend at least partially over the surface of theframe. Additional examples of frame members 230 include supportingframes, feed plates and/or gaskets. These frames, gaskets or othersupport structures may also define, at least in part, the fluid conduitsthat interconnect the membrane envelopes in an embodiment of separationassembly 20 that contains two or more membrane envelopes. Examples ofsuitable gaskets are flexible graphite gaskets, including those soldunder the trade name GRAFOIL™ by Union Carbide, although other materialsmay be used, such as depending upon the operating conditions under whichdevice 10 is used.

Continuing the above illustration of exemplary frame members 230,permeate gaskets 236 and 236′ are attached to permeate frame 232,preferably but not necessarily, by using another thin application ofadhesive. Next, membranes 46 are supported against screen structure 210and/or attached to screen structure 210 using a thin application ofadhesive, such as by spraying or otherwise applying the adhesive toeither or both of the membrane and/or screen structure. Care should betaken to ensure that the membranes are flat and firmly attached to thecorresponding screen member 212. Feed plates, or gaskets, 238 and 238′are optionally attached to gaskets 236 and 236′, such as by usinganother thin application of adhesive. The resulting membrane envelope200 is then positioned within compartment 18, such as by a suitablemount 52. Optionally, two or more membrane envelopes may be stacked orotherwise supported together within compartment 18.

As a further alternative, each membrane 46 may be fixed to a framemember 230, such as a metal frame 240, as shown in FIG. 36. If so, themembrane is fixed to the frame, for instance by ultrasonic welding oranother suitable attachment mechanism. The membrane-frame assembly may,but is not required to be, attached to screen structure 210 usingadhesive. Other examples of attachment mechanisms that achieve gas-tightseals between plates forming membrane envelope 200, as well as betweenthe membrane envelopes, include one or more of brazing, gasketing andwelding. The membrane and attached frame may collectively be referred toas a membrane plate 242. It is within the scope of the disclosure thatthe various frames discussed herein do not all need to be formed fromthe same materials and/or that the frames may not have the samedimensions, such as the same thicknesses. For example, the permeate andfeed frames may be formed from stainless steel or another suitablestructural member, while the membrane plate may be formed from adifferent material, such as copper, alloys thereof, and other materialsdiscussed in the above-incorporated patents and applicationsAdditionally and/or alternatives, the membrane plate may, but is notrequired to be, thinner than the feed and/or permeate plates.

For purposes of illustration, a suitable geometry of fluid flow throughmembrane envelope 200 is described with respect to the embodiment ofenvelope 200 shown in FIG. 35. As shown, mixed gas stream 24 isdelivered to the membrane envelope and contacts the outer surfaces 50 ofmembranes 46. The hydrogen-rich gas that permeates through the membranesenters harvesting conduit 204. The harvesting conduit is in fluidcommunication with conduits 250 through which the permeate stream may bewithdrawn from the membrane envelope. The portion of the mixed gasstream that does not pass through the membranes flows to a conduit 252through which this gas may be withdrawn as byproduct stream 36. In FIG.35, a single byproduct conduit 252 is shown, while in FIG. 36 a pair ofconduits 252 are shown to illustrate that any of the conduits describedherein may alternatively include more than one fluid passage. It shouldbe understood that the arrows used to indicate the flow of streams 34and 36 have been schematically illustrated, and that the direction offlow through conduits 250 and 252 may vary, such as depending upon theconfiguration of a particular membrane envelope 200, module 220 and/ordevice 10.

In FIG. 37, another example of a suitable membrane envelope 200 isshown. To graphically illustrate that end plates 60 and shell 62 mayhave a variety of configurations, envelope 200 is shown having agenerally rectangular configuration. The envelope of FIG. 37 alsoprovides another example of a membrane envelope having a pair ofbyproduct conduits 252 and a pair of hydrogen conduits 250. As shown,envelope 200 includes feed, or spacer, plates 238 as the outer mostframes in the envelope. Generally, each of plates 238 includes a frame260 that defines an inner open region 262. Each inner open region 262couples laterally to conduits 252. Conduits 250, however, are closedrelative to open region 262, thereby isolating hydrogen-rich stream 34.Membrane plates 242 lie adjacent and interior to plates 238. Membraneplates 242 each include as a central portion thereof ahydrogen-selective membrane 46, which may be secured to an outer frame240, which is shown for purposes of graphical illustration. In plates242, all of the conduits are closed relative to membrane 46. Eachmembrane lies adjacent to a corresponding one of open regions 262, i.e.,adjacent to the flow of mixed gas arriving to the envelope This providesan opportunity for hydrogen gas to pass through the membrane, with thenon-permeating gases, i.e., the gases forming byproduct stream 36,leaving open region 262 through conduit 252. Screen plate 234 ispositioned intermediate membranes 46 and/or membrane plates 242, i.e.,on the interior or permeate side of each of membranes 46. Screen plate234 includes a screen structure 210 or another suitable support 54.Conduits 252 are closed relative to the central region of screen plate234, thereby isolating the byproduct stream 36 and mixed gas stream 24from hydrogen-rich stream 34. Conduits 250 are open to the interiorregion of screen plate 234. Hydrogen gas, having passed through theadjoining membranes 46, travels along and through screen structure 210to conduits 250 and eventually to an output port as the hydrogen-richstream 34.

As discussed, device 10 may include a single membrane 46 within shell62, a plurality of membranes within shell 62, one or more membraneenvelopes 200 within shell 62 and/or other separation assemblies 20. InFIG. 38, a membrane envelope 200 similar to that shown in FIG. 36 isshown positioned within shell 62 to illustrate this point. It should beunderstood that envelope 200 may also schematically represent a membranemodule 220 containing a plurality of membrane envelopes, and/or a singlemembrane plate 242. Also shown for purposes of illustration is anexample of a suitable position for guide structures 144. As discussed,structures 144 also represent an example of internal supports 196. FIG.38 also illustrates graphically an example of suitable positions forports 64-68. To further illustrate suitable positions of the membraneplates and/or membrane envelopes within devices 10 containing end platesaccording to the present disclosure, FIGS. 39 and 40 respectivelyillustrate in dashed lines a membrane plate 242, membrane envelope 200and/or membrane module 220 positioned within a device 10 that includesthe end plates shown in FIGS. 21-22- and 25-26.

Shell 62 has been described as interconnecting the end plates to definetherewith internal compartment 18. It is within the scope of thedisclosure that the shell may be formed from a plurality ofinterconnected plates 230. For example, a membrane module 220 thatincludes one or more membrane envelopes 200 may form shell 62 becausethe perimeter regions of each of the plates may form a fluid-tight, orat least substantially fluid-tight seal therebetween. An example of sucha construction is shown in FIG. 41, in which a membrane module 220 thatincludes three membrane envelopes 200 is shown. It should be understoodthat the number of membrane envelopes may vary, from a single envelopeor even a single membrane plate 242, to a dozen or more. In FIG. 41, endplates 60 are schematically represented as having generally rectangularconfigurations to illustrate that configurations other than circularconfigurations are within the scope of the disclosure. It should beunderstood that the schematically depicted end plates 60 may have any ofthe end plate configurations discussed, illustrated and/or incorporatedherein.

In the preceding discussion, illustrative examples of suitable materialsof construction and methods of fabrication for the components ofhydrogen purification devices according to the present disclosure havebeen discussed. It should be understood that the examples are not meantto represent an exclusive, or closed, list of exemplary materials andmethods, and that it is within the scope of the disclosure that othermaterials and/or methods may be used. For example, in many of the aboveexamples, desirable characteristics or properties are presented toprovide guidance for selecting additional methods and/or materials. Thisguidance is also meant as an illustrative aid, as opposed to recitingessential requirements for all embodiments.

As discussed, in embodiments of device 10 that include a separationassembly that includes hydrogen-permeable and/or hydrogen-selectivemembranes 46, suitable materials for membranes 46 include palladium andpalladium alloys, including alloys containing relatively small amountsof carbon, silicon and/or oxygen. As also discussed, the membranes maybe supported by frames and/or supports, such as the previously describedframes 240, supports 54 and screen structure 210. Furthermore, devices10 are often operated at selected operating parameters that includeelevated temperatures and pressures. In such an application, the devicestypically begin at a startup, or initial, operating state, in which thedevices are typically at ambient temperature and pressure, such asatmospheric pressure and a temperature of approximately 25° C. From thisstate, the device is heated (such as with heating assembly 42) andpressurized (via any suitable mechanism) to selected operatingparameters, such as temperatures of 200° C. or more, and selectedoperating pressures, such as pressure of 50 psi or more.

When devices 10 are heated, the components of the devices will expand.The degree to which the components enlarge or expand is largely definedby the coefficient of thermal expansion (CTE) of the materials fromwhich the components are formed. Accordingly, these differences in CTEswill tend to cause the components to expand at different rates, therebyplacing additional tension or compression on some components and/orreduced tension or compression on others.

For example, consider a hydrogen-selective membrane 46 formed from analloy of 60 wt % palladium and 40 wt % copper (Pd-40Cu). Such a membranehas a coefficient of thermal expansion of 13.4 (μm/m)/° C. Furtherconsider that the membrane is secured to a structural frame 230 orretained against a support 54 formed from a material having a differentCTE than Pd-40Cu or another material from which membrane 46 is formed.When a device 10 in which these components are operated is heated froman ambient or resting configuration, the components will expand atdifferent rates. If the CTE of the membrane is less than the CTE of theadjoining structural component, then the membrane will tend to bestretched as the components are heated. In addition to this initialstretching, it should be considered that hydrogen purification devicestypically experience thermal cycling as they are heated for use, thencooled or allowed to cool when not in use, then reheated, recooled, etc.In such an application, the stretched membrane may become wrinkled as itis compressed toward its original configuration as the membrane andother structural component(s) are cooled. On the other hand, if the CTEof the membrane is greater than the CTE of the adjoining structuralcomponent, then the membrane will tend to be compressed during heatingof the device, and this compression may cause wrinkling of the membrane.During cooling, or as the components cool, the membrane is then drawnback to its original configuration.

Wrinkling of membrane 46 may cause holes and cracks in the membrane,especially along the wrinkles where the membrane is fatigued. In regionswhere two or more wrinkles intersect, the likelihood of holes and/orcracks is increased because that portion of the membrane has beenwrinkled in at least two different directions. It should be understoodthat holes and cracks lessen the selectivity of the membrane forhydrogen gas because the holes and/or cracks are not selective forhydrogen gas and instead allow any of the components of the mixed gasstream to pass thereto. During repeated thermal cycling of the membrane,these points or regions of failure will tend to increase in size,thereby further decreasing the purity of the hydrogen-rich, or permeate,stream.

One approach to guarding against membrane failure due to differences inCTE between the membranes and adjoining structural components is toplace deformable gaskets between the membrane and any component ofdevice 10 that contacts the membrane and has sufficient stiffness orstructure to impart compressive or tensile forces to the membrane thatmay wrinkle the membrane. For example, in FIG. 33, membrane 46 is shownsandwiched between feed plate 238 and permeate gasket 236, both of whichmay be formed from a deformable material. In such an embodiment and withsuch a construction, the deformable gaskets buffer, or absorb, at leasta significant portion of the compressive or tensile forces thatotherwise would be exerted upon membrane 46.

In embodiments where either or both of these frames are not formed froma deformable material (i.e., a resilient material that may be compressedor expanded as forces are imparted thereto and which returns to itsoriginal configuration upon removal of those forces), when membrane 46is mounted on a plate 242 that has a thickness and/or composition thatmay exert the above-described wrinkling tensile or compressive forces tomembrane 46, or when support 54 is bonded (or secured under the selectedoperating pressure) to membrane 46, a different approach mayadditionally or alternatively be used. More specifically, the life ofthe membranes may be increased by forming components of device 10 thatotherwise would impart wrinkling forces, either tensile or compressive,to membrane 46 from materials having a CTE that is the same or similarto that of the material or materials from which membrane 46 is formed.

For example, Type 304 stainless steel has a CTE of 17.3 and Type 316stainless steel has a CTE of 16.0. Accordingly, Type 304 stainless steelhas a CTE that is approximately 30% greater than that of Pd-40Cu, andType 316 stainless steel has a CTE that is approximately 20% greaterthan that of Pd-40Cu. This does not mean that these materials may not beused to form the various supports, frames, plates, shells and the likediscussed herein. However, in some embodiments of the disclosure, it maybe desirable to form at least some of these components form a materialthat has a CTE that is the same or similar to that of the material fromwhich membrane 46 is formed. More specifically, it may be desirable tohave a CTE that is the same as the CTE of the material from whichmembrane 46 is formed, or a material that has a CTE that is within aselected range of the CTE of the material from which membrane 46 isselected, such as within ±1%, 2%, 5%, 10%, or 15%.

In the following table, exemplary alloys and their corresponding CTE'sand compositions are presented.

TABLE 6 Alloy CTE Nominal Composition Type/Grade (μm/m/C) C Mn Ni Cr CoMo W Nb Cu Ti Al Fe Si Pd—40Cu 13.4 Monel 400 (UNS N04400) 13.9 .02 1.565 32 2.0 Monel 401 (UNS N04401) 13.7 .05 2.0 42 54 0.5 Monel 405 (UNSN04405) 13.7 .02 1.5 65 32 2.0 Monel 500 (UNS N05500) 13.7 .02 1.0 65 320.6 1.5 Type 304 Stainless 17.3 .05 1.5 9.0 19.0 Bal 0.5 (UNS S30400)Type 316 Stainless 16.0 .05 1.5 12.0 17.0 2.5 Bal 0.5 (UNS S31600) Type310S Stainless 15.9 .05 1.5 20.5 25.0 Bal 1.1 (UNS S31008) Type 330Stainless 14.4 .05 1.5 35.5 18.5 Bal 1.1 (UNS N08330) AISI Type 661Stainless 14.0 .1 1.5 20.0 21.0 20.5 3.0 2.5 1.0 31.0 0.8 (UNS R30155)Inconel 600 (UNS N06600) 13.3 .08 76.0 15.5 8.0 Inconel 601 (UNS N06601)13.75 .05 60.5 23.0 0.5 1.35 14.1 Inconel 625 (UNS N06625) 12.8 .05 61.021.5 9.0 3.6 0.2 0.2 2.5 Incoloy 800 (UNS N08800) 14.4 .05 0.8 32.5 0.40.4 0.4 46.0 0.5 Nimonic Alloy 901 (UNS N09901) 13.5 .05 42.5 12.5 6.02.7 36.2 Hastelloy X (UNS N06002) 13.3 .15 49.0 22.0 1.5 9.0 0.6 2 15.8Inconel 718 UNS N07718) 13.0 .05 52.5 19.0 3.0 5.1 0.9 0.5 18.5 Haynes230 (UNS N06002) 12.7 0.1 55.0 22.0 5.0 2.0 14 0.35 3.0

From the above information, it can be seen that alloys such as HastelloyX have a CTE that corresponds to that of Pd-40Cu, and that the Monel andInconel 601 alloys have CTE's that are within approximately 1% of theCTE of Pd-40Cu. Of the illustrative example of materials listed in thetable, all of the alloys other than Hastelloy F, Incoloy 800 and theType 300 series of stainless steel alloys have CTE's that are within 2%of the CTE of Pd-40Cu, and all of the alloys except Type 304, 316 and310 S stainless steel alloys have CTE's that are within 5% of the CTE ofPd-40Cu.

Examples of components of device 10 that may be formed from a materialhaving a selected CTE relative to membrane 46, such as a CTEcorresponding to or within one of the selected ranges of the CTE ofmembrane 46, include one or more of the following: support 54, screenmembers 212, fine or outer screen or expanded metal member 216, innerscreen member 214, membrane frame 240, permeate frame 232, permeateplate 234, feed plate 238. By the above, it should be understood thatone of the above components may be formed from such a material, morethan one of the above components may be formed from such a material, butthat none of the above components are required to be formed from such amaterial. Similarly, the membranes 46 may be formed from materials otherthan Pd-40Cu, and as such the selected CTE's will vary depending uponthe particular composition of membranes 46.

By way of further illustration, a device 10 may be formed with amembrane module 220 that includes one or more membrane envelopes 200with a screen structure that is entirely formed from a material havingone of the selected CTE's; only outer, or membrane-contacting, screenmembers (such as members 216) formed from a material having one of theselected CTE's and the inner member or members being formed from amaterial that does not have one of the selected CTE's; inner screenmember 214 formed from a material having one of the selected CTE's, withthe membrane-contacting members being formed from a material that doesnot have one of the selected CTE's, etc. By way of further illustration,a device 10 may have a single membrane 46 supported between the endplates 60 of the enclosure by one or more mounts 52 and/or one or moresupports 54. The mounts and/or the supports may be formed from amaterial having one of the selected CTE's. Similarly, at least a portionof enclosure 12, such as one or both of end plates 60 or shell 62, maybe formed from a material having one of the selected CTE's.

In embodiments of device 10 in which there are components of the devicethat do not directly contact membrane 46, these components may still beformed from a material having one of the selected CTE's. For example, aportion or all of enclosure 12, such as one or both of end plates 60 orshell 62, may be formed from a material, including one of the alloyslisted in Table 6, having one of the selected CTE's relative to the CTEof the material from which membrane 46 is formed even though theseportions do not directly contact membrane 46.

A hydrogen purification device 10 constructed according to the presentdisclosure may be coupled to, or in fluid communication with, any sourceof impure hydrogen gas. Examples of these sources include gas storagedevices, such as hydride beds and pressurized tanks. Another source isan apparatus that produces as a byproduct, exhaust or waste stream aflow of gas from which hydrogen gas may be recovered. Still anothersource is a fuel processor, which as used herein, refers to any devicethat is adapted to produce a mixed gas stream containing hydrogen gasfrom at least one feed stream containing a feedstock. Typically,hydrogen gas will form a majority or at least a substantial portion ofthe mixed gas stream produced by a fuel processor.

A fuel processor may produce mixed gas stream 24 through a variety ofmechanisms. Examples of suitable mechanisms include steam reforming andautothermal reforming, in which reforming catalysts are used to producehydrogen gas from a feed stream containing a carbon-containing feedstockand water. Other suitable mechanisms for producing hydrogen gas includepyrolysis and catalytic partial oxidation of a carbon-containingfeedstock, in which case the feed stream does not contain water. Stillanother suitable mechanism for producing hydrogen gas is electrolysis,in which case the feedstock is water. Examples of suitablecarbon-containing feedstocks include at least one hydrocarbon oralcohol. Examples of suitable hydrocarbons include methane, propane,natural gas, diesel, kerosene, gasoline and the like. Examples ofsuitable alcohols include methanol, ethanol, and polyols, such asethylene glycol and propylene glycol.

A hydrogen purification device 10 adapted to receive mixed gas stream 24from a fuel processor is shown schematically in FIG. 42. As shown, thefuel processor is generally indicated at 300, and the combination of afuel processor and a hydrogen purification device may be referred to asa fuel processing system 302. Also shown in dashed lines at 42 is aheating assembly, which as discussed provides heat to device 10 and maytake a variety of forms. Fuel processor 300 may take any of the formsdiscussed above. To graphically illustrate that a hydrogen purificationdevice according to the present disclosure may also receive mixed gasstream 24 from sources other than a fuel processor 300, a gas storagedevice is schematically illustrated at 306 and an apparatus thatproduces mixed gas stream 24 as a waste or byproduct stream in thecourse of producing a different product stream 308 is shown at 310. Itshould be understood that the schematic representation of fuel processor300 is meant to include any associated heating assemblies, feedstockdelivery systems, air delivery systems, feed stream sources or supplies,etc.

Fuel processors are often operated at elevated temperatures and/orpressures. As a result, it may be desirable to at least partiallyintegrate hydrogen purification device 10 with fuel processor 300, asopposed to having device 10 and fuel processor 300 connected by externalfluid transportation conduits. An example of such a configuration isshown in FIG. 43, in which the fuel processor includes a shell orhousing 312, which device 10 forms a portion of and/or extends at leastpartially within. In such a configuration, fuel processor 300 may bedescribed as including device 10. Integrating the fuel processor orother source of mixed gas stream 24 with hydrogen purification device 10enables the devices to be more easily moved as a unit. It also enablesthe fuel processor's components, including device 10, to be heated by acommon heating assembly and/or for at least some if not all of theheating requirements of device 10 be to satisfied by heat generated byprocessor 300.

As discussed, fuel processor 300 is any suitable device that produces amixed gas stream containing hydrogen gas, and preferably a mixed gasstream that contains a majority of hydrogen gas. For purposes ofillustration, the following discussion will describe fuel processor 300as being adapted to receive a feed stream 316 containing acarbon-containing feedstock 318 and water 320, as shown in FIG. 44.However, it is within the scope of the disclosure that the fuelprocessor 300 may take other forms, as discussed above, and that feedstream 316 may have other compositions, such as containing only acarbon-containing feedstock or only water.

Feed stream 316 may be delivered to fuel processor 300 via any suitablemechanism. A single feed stream 316 is shown in FIG. 44, but it shouldbe understood that more than one stream 316 may be used and that thesestreams may contain the same or different components. When thecarbon-containing feedstock 318 is miscible with water, the feedstock istypically delivered with the water component of feed stream 316, such asshown in FIG. 44. When the carbon-containing feedstock is immiscible oronly slightly miscible with water, these components are typicallydelivered to fuel processor 300 in separate streams, such as shown indashed lines in FIG. 44. In FIG. 44, feed stream 316 is shown beingdelivered to fuel processor 300 by a feed stream delivery system 317.Delivery system 317 includes any suitable mechanism, device, orcombination thereof that delivers the feed stream to fuel processor 300.For example, the delivery system may include one or more pumps thatdeliver the components of stream 316 from a supply. Additionally, oralternatively, system 317 may include a valve assembly adapted toregulate the flow of the components from a pressurized supply. Thesupplies may be located external of the fuel cell system, or may becontained within or adjacent the system.

As generally indicated at 332 in FIG. 44, fuel processor 300 includes ahydrogen-producing region in which mixed gas stream 24 is produced fromfeed stream 316. As discussed, a variety of different processes may beutilized in hydrogen-producing region 332. An example of such a processis steam reforming, in which region 332 includes a steam reformingcatalyst 334 and may therefore be referred to as a reforming region.Alternatively, region 332 may produce stream 24 by autothermalreforming, in which case region 332 includes an autothermal reformingcatalyst. In the context of a steam or autothermal reformer, mixed gasstream 24 may also be referred to as a reformate stream. Preferably, thefuel processor is adapted to produce substantially pure hydrogen gas,and even more preferably, the fuel processor is adapted to produce purehydrogen gas. For the purposes of the present disclosure, substantiallypure hydrogen gas is greater than 90% pure, preferably greater than 95%pure, more preferably greater than 99% pure, and even more preferablygreater than 99.5% pure. Examples of suitable fuel processors aredisclosed in U.S. Pat. No. 6,221,117, pending U.S. patent applicationSer. No. 09/802,361, which was filed on Mar. 8, 2001, and is entitled“Fuel Processor and Systems and Devices Containing the Same,” and U.S.Pat. No. 6,319,306, each of which is incorporated by reference in itsentirety for all purposes.

Fuel processor 300 may, but does not necessarily, further include apolishing region 348, such as shown in dashed lines in FIG. 44.Polishing region 348 receives hydrogen-rich stream 34 from device 10 andfurther purifies the stream by reducing the concentration of, orremoving, selected compositions therein. In FIG. 44, the resultingstream is indicated at 314 and may be referred to as a product hydrogenstream or purified hydrogen stream. When fuel processor 300 does notinclude polishing region 348, hydrogen-rich stream 34 forms producthydrogen stream 314. For example, when stream 34 is intended for use ina fuel cell stack, compositions that may damage the fuel cell stack,such as carbon monoxide and carbon dioxide, may be removed from thehydrogen-rich stream, if necessary. The concentration of carbon monoxideshould be less than 10 ppm (parts per million) to prevent the controlsystem from isolating the fuel cell stack. Preferably, the system limitsthe concentration of carbon monoxide to less than 5 ppm, and even morepreferably, to less than 1 ppm. The concentration of carbon dioxide maybe greater than that of carbon monoxide. For example, concentrations ofless than 25% carbon dioxide may be acceptable. Preferably, theconcentration is less than 10%, even more preferably, less than 1%.Especially preferred concentrations are less than 50 ppm. It should beunderstood that the acceptable minimum concentrations presented hereinare illustrative examples, and that concentrations other than thosepresented herein may be used and are within the scope of the presentdisclosure. For example, particular users or manufacturers may requireminimum or maximum concentration levels or ranges that are differentthan those identified herein.

Region 348 includes any suitable structure for removing or reducing theconcentration of the selected compositions in stream 34. For example,when the product stream is intended for use in a PEM fuel cell stack orother device that will be damaged if the stream contains more thandetermined concentrations of carbon monoxide or carbon dioxide, it maybe desirable to include at least one methanation catalyst bed 350. Bed350 converts carbon monoxide and carbon dioxide into methane and water,both of which will not damage a PEM fuel cell stack. Polishing region348 may also include another hydrogen-producing region 352, such asanother reforming catalyst bed, to convert any unreacted feedstock intohydrogen gas. In such an embodiment, it is preferable that the secondreforming catalyst bed is upstream from the methanation catalyst bed soas not to reintroduce carbon dioxide or carbon monoxide downstream ofthe methanation catalyst bed.

Steam reformers typically operate at temperatures in the range of 200°C. and 700° C., and at pressures in the range of 50 psi and 1000 psi,although temperatures outside of this range are within the scope of thedisclosure, such as depending upon the particular type and configurationof fuel processor being used. Any suitable heating mechanism or devicemay be used to provide this heat, such as a heater, burner, combustioncatalyst, or the like. The heating assembly may be external the fuelprocessor or may form a combustion chamber that forms part of the fuelprocessor. The fuel for the heating assembly may be provided by the fuelprocessing or fuel cell system, by an external source, or both.

In FIG. 44, fuel processor 300 is shown including a shell 312 in whichthe above-described components are contained. Shell 312, which also maybe referred to as a housing, enables the components of the fuelprocessor to be moved as a unit. It also protects the components of thefuel processor from damage by providing a protective enclosure andreduces the heating demand of the fuel processor because the componentsof the fuel processor may be heated as a unit. Shell 312 may, but doesnot necessarily, include insulating material 333, such as a solidinsulating material, blanket insulating material, or an air-filledcavity. It is within the scope of the disclosure, however, that the fuelprocessor may be formed without a housing or shell. When fuel processor300 includes insulating material 333, the insulating material may beinternal the shell, external the shell, or both. When the insulatingmaterial is external a shell containing the above-described reforming,separation and/or polishing regions, the fuel processor may furtherinclude an outer cover or jacket external the insulation.

It is further within the scope of the disclosure that one or more of thecomponents of fuel processor 300 may either extend beyond the shell orbe located external at least shell 312. For example, device 10 mayextend at least partially beyond shell 312, as indicated in FIG. 43. Asanother example, and as schematically illustrated in FIG. 44, polishingregion 348 may be external shell 312 and/or a portion ofhydrogen-producing region 312 (such as portions of one or more reformingcatalyst beds) may extend beyond the shell.

As indicated above, fuel processor 300 may be adapted to deliverhydrogen-rich stream 34 or product hydrogen stream 314 to at least onefuel cell stack, which produces an electric current therefrom. In such aconfiguration, the fuel processor and fuel cell stack may be referred toas a fuel cell system. An example of such a system is schematicallyillustrated in FIG. 45, in which a fuel cell stack is generallyindicated at 322. The fuel cell stack is adapted to produce an electriccurrent from the portion of product hydrogen stream 314 deliveredthereto. In the illustrated embodiment, a single fuel processor 300 anda single fuel cell stack 322 are shown and described, however, it shouldbe understood that more than one of either or both of these componentsmay be used. It should also be understood that these components havebeen schematically illustrated and that the fuel cell system may includeadditional components that are not specifically illustrated in thefigures, such as feed pumps, air delivery systems, heat exchangers,heating assemblies and the like.

Fuel cell stack 322 contains at least one, and typically multiple, fuelcells 324 that are adapted to produce an electric current from theportion of the product hydrogen stream 314 delivered thereto. Thiselectric current may be used to satisfy the energy demands, or appliedload, of an associated energy-consuming device 325. Illustrativeexamples of devices 325 include, but should not be limited to, a motorvehicle, recreational vehicle, boat, tools, lights or lightingassemblies, appliances (such as household or other appliances),household, signaling or communication equipment, etc. It should beunderstood that device 325 is schematically illustrated in FIG. 45 andis meant to represent one or more devices or collection of devices thatare adapted to draw electric current from the fuel cell system. A fuelcell stack typically includes multiple fuel cells joined togetherbetween common end plates 323, which contain fluid delivery/removalconduits (not shown). Examples of suitable fuel cells include protonexchange membrane (PEM) fuel cells and alkaline fuel cells. Fuel cellstack 322 may receive all of product hydrogen stream 314. Some or all ofstream 314 may additionally, or alternatively, be delivered, via asuitable conduit, for use in another hydrogen-consuming process, burnedfor fuel or heat, or stored for later use.

The above-identified and incorporated patents and patent applicationscontain numerous examples of fuel processors according to the presentdisclosure. For purposes of illustration, representative examples ofsteam reformers with separation regions that include one or moremembranes 46 according to the present disclosure are shown. In view ofthe preceding incorporations by reference, each component, subcomponent,and variation will not be represented and discussed below and/orindicated with reference numbers in the subsequently described figures.Similarly, where possible, like reference numbers will be used. Itshould be understood that the following discussion is intended toprovide exemplary constructions for steam reformers according to thepresent disclosure, and that any of the above-described features,elements, subelements and/or variations may be incorporated into any ofthese reformers.

FIG. 46 illustrates in cross section an illustrative example of a fuelprocessor 300 in the form of a steam reformer 400. In FIG. 46, reformer400 includes a shell 312, which as indicated has a generally closed-endtubular structure. Shell 312 receives through inlet 434 an air supplyand releases at combustion ports 438 combustion byproducts. Reformer 400is heated by a heating assembly 42 in the form of a combustion region460 that contains a combustion catalyst 462. As illustrated somewhatschematically, catalyst 462 is located generally toward inlet 434, butit is within the scope of the disclosure that the catalyst mayadditionally or alternatively be located elsewhere within, or evenexternal, shell 312. Examples of suitable combustion catalyst materialsinclude platinum supported on alumina or other inert andthermally-stable ceramic. As shown, feed stream 316 is delivered to thereformer at an inlet 430, which is in communication with a coil 430 a inwhich the feedstock is vaporized. As such, reformer 400 may be describedas including a vaporization region 432.

Within reforming region 332 a reforming catalyst 334 (e.g., BASFcatalyst K3-110 or ICI catalyst 52-8) reacts with the vaporized feedstream to produce mixed gas stream 24 in the vicinity of a separationregion that contains a hydrogen-selective membrane 46. As discussed,membrane 46 may have any of the compositions and constructions describedand incorporated herein, including the relatively low carbon contentconstruction described above. As shown, membrane 46 includes end caps436 and is supported by a support 54 in the form of a tension spring 58.

As discussed previously, hydrogen-rich stream 34 is formed from theportion of mixed gas stream 24 that passes through membrane 46, with theremaining portion of the mixed gas stream forming byproduct stream 36.Hydrogen-rich stream 34 travels within permeate region 32, which asillustrated within tubular membrane 46 may be described as a transportregion to a polishing region 348, which in the illustrated embodiment iscontained at least partially within region 32. As shown, region 348contains both a reforming catalyst bed, or region, 352 downstream ofmembrane 46, as well as a methanation catalyst bed, or region, 350downstream from the reforming catalyst bed. As discussed, the catalystbeds or regions may form part of a single catalyst bed or may bespaced-apart from each other. Similarly, the beds may vary in relativesize and number. Also shown for purposes of illustration in FIG. 41 isanother example of a heating assembly 42, namely, an electric resistanceheater 442. As shown, heater 442 is located within permeate region 32.However, other placements are possible and within the scope of thedisclosure, such as within reforming region 332.

As discussed, byproduct stream 36 may contain hydrogen and other gasesthat may be used or stored for other applications, including as acombustion fuel to provide some or all of the heating requirements ofreformer 400. In the illustrated embodiment, reformer 400 is configuredso that stream 36 flows into combustion region 460 and is ignited by acombustion catalyst 462.

FIG. 47 illustrates schematically the architecture of an alternatereformer 400′ with an enlarged outermost metal shell 312′ that defines acommon combustion region 460′. Within the relatively larger combustionregion 460′, a plurality of reforming assemblies 451 are arranged inspaced relation. The reforming assemblies may have the same or similarconstructions, such as each including a reforming region 332, separationassembly (such as with one or more membranes 46), and in someembodiments a polishing, or purification, region 348. While not shown inFIG. 47 for purposes of clarity, reformer 400′ includes a feedstockinlet, a product hydrogen outlet, and a byproduct or exhaust gas outlet.As shown, a common air inlet 434 supplies air to the common combustionregion 460′. As may be appreciated, each of reforming assemblies 451provides a byproduct stream 36 to the combustion region 460′.

FIG. 48 illustrates in partial cross-section, another example of a fuelprocessor 300 in the form of a steam reformer, which is generallyindicated at 400. ″Reformer 400″ demonstrates another example of areformer having a heating assembly 42 in the form of acatalytically-ignited combustion region 460 distributed throughreforming region 332 to improve heat transfer from the combustionprocess to the reformation process. As shown for purposes ofillustration in FIG. 48, reformer 400″ also includes a purificationassembly, or polishing region, 348.

Reformer 400″ includes an outer shell 312 sealed at each end by endplates 453. As shown, bolts are used to secure the end plates to theshoulders, or flanges, of a tubular portion of shell 312. However, it iswithin the scope of the disclosure that other fastening mechanisms maybe used and that at least one of the end plates may be integrally formedwith the rest of the shell. To illustrate that a variety of internalconfigurations are possible for reformers according to the presentdisclosure, reformer 400″ includes a reforming region 332 through whicha tubular combustion region 460 extends, in contrast to the tubularreforming region within a combustion region shown in FIG. 46. While acoil or spiral form of combustion system has been illustrated, i.e., thecoil 430 a, other shapes may be employed as a combustion system withinthe reforming region 332.

Reformer 400″ also demonstrates that one or more of the reformers fluidconduits may extend external shell 312. For example, reformer 400″includes a conduit 470 through which byproduct stream 36 flows. In theillustrated embodiment, conduit 470 includes a valve assembly 473, whichmay include a pressure let-down valve and/or other types of flowregulating valves to deliver stream 36 at the desired pressure forutilization as a combustion fuel within the pressurized reformer. Asshown, conduit 470 delivers stream 36 to an intake manifold 477.Manifold 477 includes an air inlet 434, e.g., coupled to an air bloweror to discharged air from the cathode component of a fuel cell stack orto another suitable air source, and air passage way 471 in which the airand fuel stream are mixed and which is in communication with combustionregion 460, which as shown has a coiled configuration. In FIG. 48,combustion region 460 again illustrates the use of a combustion catalyst462, although other combustion sources, such as spark plugs, pilots,glow plugs, and the like may be used. As shown in dashed lines at 478 inFIG. 48, reformer 400 may receive some or all of its combustible fuelfrom an external source. However, and as discussed in more detail in theincorporated applications byproduct stream 36 may additionally oralternatives form at least a portion of the combustible fuel stream.

FIG. 49 illustrates another example of a fuel processor in the form of asteam reformer, which is generally indicated at 500. Reformer 500demonstrates an example of a reformer having a vaporization region 432that is generally isolated, other than the conduit that delivers thevaporized feed stream, from reforming region 332. Expressed another way,reformer 500 includes a partition 510 that at least substantiallyseparates the vaporization and reforming regions. In the illustratedembodiment, vaporization region 432 (and coil 430 a) are at leastsubstantially contained within combustion region 460, although it iswithin the scope of the disclosure that both the combustion andvaporization regions may be separated from the reforming region and fromeach other. However, in many embodiments, the vaporization andcombustion regions will be at least partially coextensive to reduce theheat requirements or heat transfer requirements of the reformer. In theillustrated embodiment, combustion region 460 contains an ignitionsource in the form of a spark plug 502 and delivers heated combustiongases through conduits 504 that extend through partition 510 and atleast partially through reforming region 332.

Reformer 500 also demonstrates an example of a steam reformer (or fuelprocessor) utilizing an attached hydrogen-purification device 10 in theform of a separation assembly 20 containing a plurality of at leastgenerally planar hydrogen-selective membranes 46 and/or membraneenvelopes. As discussed, membranes 46 may have a variety of compositionsand constructions, including the relatively low carbon-content membranes(such as Pd-40Cu or other palladium or palladium alloy membranes)discussed above. As shown, conduit 470 delivers byproduct stream 36 tointake manifold 477.

In FIG. 50, another embodiment of the fuel processor in the form of asteam reformer is shown and generally indicated at 500′. Similar to thepreviously described embodiments, reformer 500′ includes a shell 312that houses a reforming region 332 and a combustion region 460. In theillustrated embodiment, reformer 500′ includes a plurality of reformingtubes, or regions, 530 that each contain reforming catalyst 334. Threesuch tubes are shown in FIG. 50, and it should be understood that, likethe rest of the reformers disclosed herein, reformer 500′ may include asfew as one tube or region and in many embodiments may include multipletubes, such as six, ten or more tubes. Understandably, the number oftubes in any particular embodiment may vary, depending upon such factorsas the size of the reformer's shell, the desired rate of hydrogenproduction, and the number of additional elements within the shell. Forexample, when a plate-type membrane module is used, there is typicallymore available space within a similarly sized shell 312 than when atubular membrane is used.

Reformer 500′ also provides an illustrative example of a reformer inwhich at least a portion of the reforming region extends beyond shell312. As shown in FIG. 50, a portion 532 of each reforming tube 530extends external shell 312. This enables the tubes (and the reformingcatalyst contained therein) to be accessed without having to open theshell. In this configuration each end portion 532 includes a removablecap or other closure which may be selectively removed to permit accessto the interior of the tube, and thereafter replaced. This configurationfor the reforming tubes may be used with any of the other reformersdisclosed herein, just as reformer 500′ may include reforming tubeswhich are completely housed within shell 312.

In the illustrated embodiment, tubes 530 are heated by hot combustiongases passing from internal combustion manifold 534 to internal exhaustmanifold 536, and ultimately exiting reformer 500′ through outlet 438.In FIG. 50, a plurality of passages 538 are shown which permit the hotcombustion gases to pass between manifolds 534 and 536, and thereby heattubes 530 as the gases flow around the tubes. Hot combustion gases areproduced by a heating assembly 42, which in the illustrated embodimentmay be described as a burner 503. Upon initial startup, burner 503 isignited by a suitable ignition source, such as spark plug 502, or any ofthe other ignition sources disclosed herein. Combustion air, preferablyat or near ambient pressure, is delivered to burner 503 through airinlet 434. Feed stream 316 for the steam reforming process is admittedinto the fuel processor through inlet tube 430 and is vaporized as it isheated by the combustion gases. As discussed, a single inlet tube 430may be used to admit a feedstock comprising alcohol and water, ormultiple separate inlet tubes may be used (such as disclosed herein) ifthe feedstock consists of separate streams of water and a hydrocarbon oralcohol. As shown in FIG. 50, inlet tube 430 forms a coil 430 a thatdefines at least a portion of a vaporization region 432. As shown, coil430 a extends around tubes 530 multiple times before entering adistribution manifold 528. When tubes 530 are of similar size or areadapted to process generally equal volumes of feeds, the feedstock isevenly distributed between the tubes by manifold 528. However, thefeedstock may be otherwise proportioned if the tubes are adapted toreceive and process different flows of the feedstock.

Coil 430 a should be of sufficient length that the feedstock isvaporized prior to reaching distribution manifold 528. It should beunderstood that the circuitous path of coil 430 a is shown in FIG. 50for purposes of illustrating one possible path. The important concern isthat the coil is of sufficient length that the feedstock passingtherethrough is vaporized by heat transmitted to it as it travels todistribution manifold 528. To aid with the vaporization of thefeedstock, multiple coils of tubing may be used to effectively increasethe heat transfer surface area of the tubing, and thereby aid in thevaporization of the feedstock. Vaporization of the feedstock may also beaccomplished using plate-type vaporizers, isolated vaporization regions,heating assemblies that vaporize the feed stream prior to delivery tothe reformer, etc.

From distribution manifold 528, the vaporized feedstock is distributedto steam reforming tubes 530 and the mixed gas streams 24 generatedtherein are delivered to a separation assembly, which in the illustratedembodiment takes the form of a membrane module having a plurality ofmembrane envelopes 200 that each contain hydrogen-selective membranes46.

Reformer 500″ includes the previously described conduit 470, which asdiscussed may be configured to deliver at least a portion of stream 36to combustion region 460. Also shown in FIG. 50 are other non-essentialelements that may be used within any of the reformers and/or fuelprocessors disclosed herein. For example, in FIG. 50, reformer 500′further includes a pressure gauge 542 for monitoring the pressure of thefuel gas in conduit 471, a pressure relief valve 544, and a vent valve546. Also illustrated are a valve 548, which controls the flow of fuelgas in conduit 471 to the burner and applies back pressure on thereforming region, and a valve 549, which controls the flow of start-upfuel gas (previously produced and stored or supplied from an externalsource), such as hydrogen, propane or natural gas, during a coldstart-up of the reformer.

To illustrate another example of a portion of the reformer being locatedexternal shell 312, reformer 500′ is shown with a polishing region 348located external shell 312. As shown, region 348 extends proximate theexterior surface 540 of shell 312. However, it is within the scope ofthe disclosure that region 348 may be at least partially or completelypositioned against or spaced away from shell 312. Polishing region 348is further heated by the hydrogen-rich stream 24 that flows into the bedfrom the separation region 20. Finally, purified hydrogen exits reformer500′ as stream 314. By locating the polishing catalyst bed externalshell 312, reformer 500′ may either include additional reforming tubeswithin its shell, or the shell may be smaller because it no longer needsto house the polishing catalyst bed.

In FIG. 51, a variation of the reformer of FIG. 50 is shown andgenerally indicated at 500″. To provide more space within shell 312, andthereby permit additional reforming tubes 530 to be housed therein orpermit shell 312 to be smaller, reformer 500″ includes vaporizationcoils 552 which are located external shell 312. As shown, coils 552 arewrapped around the external surface 540 of shell 312 and are in contacttherewith. Similar to the polishing catalyst bed described with respectto FIG. 51, coils 552 may be at least partially or completely spacedapart from shell 312. In this case, the important factor is thatsufficient heat is transmitted to the feedstock within the coils tovaporize the feedstock before it reaches reforming region 332. In theposition shown in FIG. 51, the coils are heated by radiation and thermalconduction from the hot surface of shell 312.

The reformer shown in FIG. 51 also demonstrates an example of suitablestructure for admitting to the reforming region feed streams 316 thatcontain immiscible components. As shown, reformer 500″ includes an inlettube 554 through which a water feed is received and delivered tovaporization region 432 having vaporization coils 552. A hydrocarbon oralcohol feed is admitted through inlet tube 556, and it is mixed withthe hot steam before passing into the reformer through a reformer inlettube 558. The combined feedstock stream passes into one end of a mixingchamber 560, which contains an optional static mixer or a packing (notshown) to promote turbulent flow and thereby encourage mixing of thevaporized feedstocks. The mixed, vaporized feedstock exit the mixingchamber and are delivered to distribution manifold 561, which in turndistributes the feedstock to the reforming tubes.

To increase the energy efficiency and to increase the combustion chambertemperature within the reformer, reformer 500″ includes a quenchingchamber 562 adapted to partially quench the reformate gas stream priorto its entrance into separation region 20, which as discussed maycontain one or more membranes 46 and/or membrane envelopes 200. Asshown, the reformate gas stream must pass through chamber 562 afterexiting reforming tubes 530 and prior to entering region 20. Chamber 562includes a pair of ports 564 and 566 through which combustion airrespectively enters and exits the chamber. The air is cooler than thereformate gas stream, and therefore cools the reformate gas stream priorto its entry into the separation region. During this exchange, thecombustion air is heated prior to its entry to burner 503.

The quenching chamber and external vaporization coils described withrespect to reformer 500″ may be used with any of the reformers (or fuelprocessors) described, illustrated and/or incorporated herein.Similarly, the external polishing catalyst bed may be used with any ofthe reformers described herein, such as to increase the number ofreforming tubes within the reformer's shells or to decrease the size ofthe shell.

INDUSTRIAL APPLICABILITY

The invented hydrogen purification membranes, devices and fuelprocessing systems are applicable to the fuel processing, fuel cell andother industries in which hydrogen gas is produced and/or utilized.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. Similarly, where theclaims recite “a” or “a first” element or the equivalent thereof, suchclaims should be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.

It is believed that the following claims particularly point out certaincombinations and subcombinations that are directed to one of thedisclosed inventions and are novel and non-obvious. Inventions embodiedin other combinations and subcombinations of features, functions,elements and/or properties may be claimed through amendment of thepresent claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

1. A hydrogen-producing fuel processing assembly, comprising: ahydrogen-producing region adapted to produce a mixed gas stream from atleast one feed stream, wherein the mixed gas stream includes hydrogengas as a majority component and other gases; an enclosure defining aninternal compartment having an internal surface; a separation assemblywithin the internal compartment, wherein the separation assembly isadapted to receive a mixed gas stream and to divide the mixed gas streaminto a hydrogen-rich permeate stream, which has a greater concentrationof hydrogen gas than the mixed gas stream, and a byproduct stream, whichcomprises a greater concentration of the other gases than the mixed gasstream, and further wherein the separation assembly comprises: at leastone hydrogen-selective membrane having a mixed gas surface and apermeate surface, wherein the permeate stream includes hydrogen gas thatpermeates through the membrane from the mixed gas surface to thepermeate surface, and further wherein the byproduct stream includes atleast a portion of the mixed gas stream that does not permeate throughthe membrane; a support structure for the at least onehydrogen-selective membrane; and at least one guide structure projectingfrom the enclosure into the internal compartment to define a positionfor the separation assembly within the internal compartment.
 2. Theassembly of claim 1, wherein the device includes a plurality of guidestructures that project into the internal compartment to define theposition of the separation assembly within the internal compartment. 3.The assembly of claim 1, wherein the guide structure includes a rib thatprojects into the internal compartment.
 4. The assembly of claim 1,wherein the enclosure is formed from a material, and further wherein theguide structure is formed from the same material as the enclosure. 5.The assembly of claim 4, wherein the guide structure is integrallyformed with the enclosure.
 6. The assembly of claim 1, wherein theseparation assembly includes a plurality of hydrogen-selectivemembranes.
 7. The assembly of claim 1, wherein the separation assemblyincludes at least a plurality of hydrogen-selective membranes, eachhaving a mixed gas surface and a permeate surface, wherein thehydrogen-selective membranes are spaced-apart from each other andoriented with their permeate surfaces generally facing each other todefine a harvesting conduit extending therebetween, and further whereinthe permeate stream is formed from at least a portion of the mixed gasstream that passes through the hydrogen-selective membranes to theharvesting conduit, with the byproduct stream being formed from at leasta portion of the mixed gas stream that remains on the mixed gas surfaceof the hydrogen-selective membranes, wherein the separation assemblyfurther includes a support within the harvesting conduit and adapted tosupport the plurality of hydrogen-selective membranes, and furtherwherein the support includes a pair of generally opposed surfaces whichare adapted to provide support to a respective one of the permeatesurfaces of the hydrogen-selective membranes.
 8. The assembly of claim7, wherein the support is adapted to permit flow of gas both paralleland transverse to the permeate surfaces of the membranes.
 9. Theassembly of claim 1, wherein the enclosure includes an input portadapted to receive the mixed gas stream from the hydrogen-producingregion.
 10. The assembly of claim 1, wherein the hydrogen-producingregion is located within the internal compartment, and further whereinthe enclosure includes an input port adapted to receive the at least onefeed stream.
 11. The assembly of claim 1, further comprising avaporization region adapted to receive and vaporize a liquid feed streamcomprising a carbon-containing feedstock and water.
 12. The assembly ofclaim 1, further comprising a polishing catalyst bed including amethanation catalyst, wherein the polishing catalyst bed is in fluidcommunication with the separation assembly and is adapted to receive thehydrogen-rich permeate stream therefrom and produce a product streamfrom the hydrogen-rich permeate stream, wherein the polishing catalystbed is adapted to reduce the concentration of carbon dioxide and carbonmonoxide in the hydrogen-rich permeate stream by catalytic reaction toproduce methane.
 13. The assembly of claim 12, wherein the polishingcatalyst bed is at least partially located within the internalcompartment of the enclosure.
 14. The assembly of claim 13, wherein aportion of the polishing catalyst bed extends external the internalcompartment of the enclosure.
 15. The assembly of claim 12, wherein thepolishing catalyst bed is located external the internal compartment ofthe enclosure.
 16. The assembly of claim 1, wherein the separationassembly is adapted to produce a byproduct stream containingapproximately 20-50% of the stoichiometrically available hydrogen gas inthe mixed gas stream.
 17. The assembly of claim 1, wherein the amount ofhydrogen gas in the hydrogen-rich permeate stream is less than astoichiometrically available amount of hydrogen gas.
 18. The assembly ofclaim 1, wherein the amount of hydrogen gas in the hydrogen-richpermeate stream is between approximately 50% and approximately 80% ofthe stoichiometrically available hydrogen gas in the mixed gas stream.19. The assembly of claim 1, further comprising a heating assembly thatincludes a combustion region adapted to receive and combust a fuelstream to produce a heated exhaust stream to heat the hydrogen-producingregion.
 20. The assembly of claim 1, wherein the fuel stream is at leastpartially comprised of the byproduct stream, and further wherein thebyproduct stream contains at least 20 wt % hydrogen gas.
 21. Theassembly of claim 1, in combination with a fuel cell stack adapted toreceive at least a portion of the hydrogen-rich permeate stream and toproduce an electric current therefrom.
 22. The assembly of claim 21,wherein the combustion region is adapted to receive air for supportingcombustion from the fuel cell stack.